THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 


PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


PALCONTOLO 


•MUM 

SCONCES 
LIBRARY 


GEOLOGICAL    SKETCHES. 


BY 


L.    AGASSIZ. 


BOSTON: 
TICK  NOR      AND      FIELDS 

1866. 


PALEONTOLOGY  LIBRARY 
Gift  of  C.  A.  Kofoid 


Entered  according  to  Act  of  Congress,  in  the  year  1866,  by 

TICKNOR     AND     FIELDS, 
in  the  Clerk's  Office  of  the  District  Court  of  the  District  of  Massachusetts. 


UNIVERSITY  PRESS  :  WELCH,  BIGELOW,  &  Co., 
CAMBRIDGE. 


V  t 

' 


PREFACE. 


THE  articles  collected  in  this  volume,  like  those 
formerly  published  under  the  title  of  "  Methods 
of  Study,"  were  originally  prepared  from  notes 
of  extemporaneous  lectures,  and  first  appeared 
in  the  pages  of  the  Atlantic  Monthly.  They  still 
retain  something  of  the  familiarity  induced  by 
the  personal  relation  of  a  lecturer  to  his  audi- 
ence, so  different  from  the  more  distant  one  of 
the  author  to  his  reading  public.  They  must 
indeed  be  considered  as  familiar  talks  on  scien- 
tific subjects  rather  than  as  scientific  papers. 

The  three  concluding  chapters  on  Glaciers  are 
introduced  with  special  reference  to  their  geologi- 
cal significance,  and  will  be  followed  in  a  future 
volume  by  a  number  of  articles  showing  the 
former  extension  of  glaciers  on  this  continent 
as  well  as  in  Europe,  and  giving  at  some  length 
the  history  of  their  retreat.  This  will  naturally 


iv  PEEFACE. 

lead  to  a  discussion  of  all  the  facts  connected 
with  the  ice  period,  the  erratic  boulders,  the 
drift,  the  formation  of  river  systems,  ancient  lake 
and  river  terraces, —  all  the  phenomena,  in  short, 
resulting  from  the  former  presence  of  such  im- 
mense masses  of  ice  and  their  subsequent  disap- 
pearance. These  questions  have  been  chiefly 
studied  on  the  European  continent,  where  the 
broken  character  of  the  country,  intersected  in 
every  direction  by  mountain  chains,  presents  nu- 
merous centres  of  dispersion  for  glaciers.  Owing 
to  the  extensive  land  surfaces  on  this  continent, 
the  same  set  of  facts  presents  quite  a  different 
aspect  here  and  in  the  Old  World ;  and  I  hope 
that  the  facilities  I  have  had  for  tracing  the  gla- 
cial phenomena  in  America  may  enable  me  to 
throw  some  new  light  on  this  subject. 

L.   AGASSIZ. 

CAMBRIDGE,  November  29th,  1865. 


CONTENTS. 


PAGB 

I.    AMERICA  THE  OLD  WORLD      ....  1 

II.    THE  SILURIAN  BEACH  .....  29 

III.  THE   FERN    FORESTS   OF  THE  CARBONIFEROUS 

PERIOD         .......  64 

IV.  MOUNTAINS  AND  THEIR  ORIGIN    ...  94 
V.    THE  GROWTH  OF  CONTINENTS         .         .         .120 

VI.    THE  GEOLOGICAL  MIDDLE  AGE  ...  148 
VII.    THE  TERTIARY  AGE,  AND  ITS  CHARACTERISTIC 

ANIMALS 181 

VIII.    THE  FORMATION  OF  GLACIERS     .         .         .  208 
IX.    INTERNAL    STRUCTURE    AND    PROGRESSION    OF 

GLACIERS 233 

X.    EXTERNAL  APPEARANCE  OF  GLACIERS  .  283 


I. 

AMERICA  THE  OLD  WORLD. 

FIRST-BORN  among  the  Continents,  though 
so  much  later  in  culture  and  civilization  than 
some  of  more  recent  birth,  America,  so  far  as  her 
physical  history  is  concerned,  has  been  falsely  de- 
nominated the  New  World.  Hers  was  the  first  dry 
land  lifted  out  of  the  waters,  hers  the  first  shore 
washed  by  the  ocean  that  enveloped  all  the  earth 
beside ;  and  while  Europe  was  represented  only 
by  islands  rising  here  and  there  above  the  sea, 
America  already  stretched  an  unbroken  line  of 
land  from  Nova  Scotia  to  the  Far  West.* 

In  the  present  state  of  our  knowledge,  our  con- 
clusions respecting  the  beginning  of  the  earth's 
history,  the  way  in  which  it  took  form  and  shape 
as  a  distinct,  separate  planet,  must,  of  course,  be 
very  vague  and  hypothetical.  Yet  the  progress 

*  It  would  be  inexpedient  to  encumber  these  pages  with  ref- 
erences to  all  the  authorities  on  which  such  geological  results 
rest.  They  are  drawn  from  the  various  State  Surveys,  including 
that  of  the  mineral  lands  of  Lake  Superior,  in  which  the  early 
rise  of  the  American  Continent  is  for  the  first  time  affirmed,  and 
other  more  general  works  on  American  geology. 

1  A 


2  AMERICA  THE   OLD  WORLD. 

of  science  is  so  rapidly  reconstructing  the  past 
that  we  may  hope  to  solve  even  this  problem; 
and  to  one  who  looks  upon  man's  appearance 
upon  the  earth  as  the  crowning  work  in  a  suc- 
cession of  creative  acts,  all  of  which  have  had 
relation  to  his  coming  in  the  end,  it  will  not 
seem  strange  that  he  should  at  last  be  allowed 
to  understand  a  history  which  was  but  the  intro- 
duction to  his  own  existence.  It  is  my  belief 
that  not  only  the  future,  but  the  past  also,  is  the 
inheritance  of  man,  and  that  we  shall  yet  con- 
quer our  lost  birthright. 

Even  now  our  knowledge  carries  us  far  enough 
to  warrant  the  assertion  that  there  was  a  time 
when  our  earth  was  in  a  state  of  igneous  fusion, 
when  no  ocean  bathed  it  and  no  atmosphere  sur- 
rounded it,  when  no  wind  blew  over  it  and  no 
rain  fell  upon  it,  but  an  intense  heat  held  all  its 
materials  in  solution.  In  those  days  the  rocks 
which  are  now  the  very  bones  and  sinews  of 
our  mother  Earth  —  her  granites,  her  porphy- 
ries, her  basalts,  her  syenites  —  were  melted  into 
a  liquid  mass.  As  I  am  writing  for  the  unscien- 
tific reader,  who  may  not  be  familiar  with  the 
facts  through  which  these  inferences  have  been 
reached,  I  will  answer  here  a  question  which, 
were  we  talking  together,  he  might  naturally  ask 
in  a  somewhat  skeptical  tone.  How  do  you 
know  that  this  state  of  things  ever  existed,  and, 


AMERICA  THE  OLD  WORLD.  3 

supposing  that  the  solid  materials  of  which  our 
earth  consists  were  ever  in  a  liquid  condition, 
what  right  have  you  to  infer  that  this  condition 
was  caused  by  the  action  of  heat  upon  them  ? 
I  answer,  Because  it  is  acting  upon  them  still ; 
because  the  earth  we  tread  is  but  a  thin  crust 
floating  on  a  liquid  sea  of  molten  materials ; 
because  the  agencies  that  were  at  work  then  are 
at  work  now,  and  the  present  is  the  logical 
sequence  of  the  past.  From  Artesian  wells,  from 
mines,  from  geysers,  from  hot  springs,  a  mass 
of  facts  has  been  collected,  proving  incontestably 
the  heated  condition  of  all  substances  at  a  certain 
depth  below  the  earth's  surface ;  and  if  we  need 
more  positive  evidence,  we  have  it  in  the  fiery 
eruptions  that  even  now  bear  fearful  testimony  to 
the  molten  ocean  seething  within  the  globe  and 
forcing  its  way  out  from  time  to  time.  The 
modern  progress  of  Geology  has  led  us  by  suc- 
cessive and  perfectly  connected  steps  back  to  a 
time  when  what  is  now  only  an  occasional  and 
rare  phenomenon  was  the  normal  condition  of 
our  earth ;  when  those  internal  fires  were  en- 
closed in  an  envelop  so  thin  that  it  opposed  but 
little  resistance  to  their  frequent  outbreak,  and 
they  constantly  forced  themselves  through  this 
crust,  pouring  out  melted  materials  that  sub- 
sequently cooled  and  consolidated  on  its  surface. 
So  constant  were  these  eruptions,  and  so  slight 


4  AMERICA  THE   OLD  WORLD. 

was  the  resistance  they  encountered,  that  some 
portions  of  the  earlier  rock-deposits  are  perfo- 
rated with  numerous  chimneys,  narrow  tunnels 
as  it  were,  bored  by  the  liquid  masses  that  poured 
out  through  them  and  greatly  modified  their  first 
condition. 

The  question  at  once  suggests  itself,  How  was 
even  this  thin  crust  formed  ?  what  should  cause 
any  solid  envelope,  however  slight  and  filmy 
when  compared  to  the  whole  bulk  of  the  globe, 
to  form  upon  the  surface  of  such  a  liquid  mass  ? 
At  this  point  of  the  investigation  the  geologist 
must  appeal  to  the  astronomer ;  for  in  this  vague 
and  nebulous  border-land,  where  the  very  rocks 
lose  their  outlines  and  flow  into  each  other, 
not  yet  specialized  into  definite  forms  and  sub- 
stances. —  there  "the  two  sciences  meet.  Astron- 
omy shows  us  our  planet  thrown  off  from  the 
central  mass  of  which  it  once  formed  a  part,  to 
move  henceforth  in  an  independent  orbit  of  its 
own.  That  orbit,  it  tells  us,  passed  through 
celestial  spaces  cold  enough  to  chill  this  heated 
globe,  and  of  course  to  consolidate  it  externally. 
We  know,  from  the  action  of  similar  causes  on  a 
smaller  scale  and  on  comparatively  insignificant 
objects  immediately  about  us,  what  must  have 
been  the  effect  of  this  cooling  process  upon  the 
heated  mass  of  the  globe.  All  substances  when 
heated  occupy  more  space  than  they  do  when 


AMEEICA   THE   OLD  WORLD.  5 

cold.  Water,  which  expands  when  freezing,  is 
the  only  exception  to  this  rule.  The  first  effect 
of  cooling  the  surface  of  our  planet  must  have 
been  to  solidify  it,  and  thus  to  form  a  film  or 
crust  over  it.  That  crust  would  shrink  as  the 
cooling  process  went  on ;  in  consequence  of  the 
shrinking,  wrinkles  and  folds  would  arise  upon 
it,  and  here  and  there,  where  the  tension  was  too 
great,  cracks  and  fissures  would  be  produced. 
In  proportion  as  the  surface  cooled,  the  masses 
within  would  be  affected  by  the  change  of  tem- 
perature outside  of  them,  and  would  consolidate 
internally  also,  the  crust  gradually  thickening  by 
this  process. 

But  there  was  another  element  without  the 
globe,  equally  powerful  in  building  it  up.  Fire 
and  water  wrought  together  in  this  work,  if  not 
always  harmoniously,  at  least  with  equal  force 
and  persistency.  I  have  said  that  there  was  a 
time  when  no  atmosphere  surrounded  the  earth ; 
but  one  of  the  first  results  of  the  cooling  of  its 
crust  must  have  been  the  formation  of  an  atmos- 
phere, with  all  the  phenomena  connected  with 
it,  —  the  rising  of  vapors,  their  condensation  into 
clouds,  the  falling  of  rains,  the  gathering  of 
waters  upon  its  surface.  Water  is  a  very  active 
agent  of  destruction,  but  it  works  over  again  the 
materials  it  pulls  down  or  wears  away,  and  builds 
them  up  anew  in  other  forms.  As  soon  as  an 


6  AMERICA   THE   OLD   WORLD. 

ocean  washed  over  the  consolidated  crust  of  the 
globe,  it  would  begin  to  abrade  the  surfaces  upon 
which  it  moved,  gradually  loosening  and  detach- 
ing materials,  to  deposit  them  again  as  sand  or 
mud  or  pebbles  at  its  bottom  in  successive  layers, 
one  above  another.  Thus,  in  analyzing  the  crust 
of  the  globe,  we  find  at  once  two  kinds  of  rocks, 
the  respective  work  of  fire  and  water :  the  first 
poured  out  from  the  furnaces  within,  and  cool- 
ing, as  one  may  see  any  mass  of  metal  cool  that 
is  poured  out  from  a  smelting-furnace  to-day, 
in  solid  crystalline  masses,  without  any  division 
into  separate  layers  or  leaves ;  and  the  latter  in 
successive  beds,  one  over  another,  the  heavier 
materials  below,  the  lighter  above,  or  sometimes 
in  alternate  layers,  as  special  causes  may  have 
determined  successive  deposits  of  lighter  or  heav- 
ier materials  at  some  given  spot. 

There  were  many  well-fought  battles  between 
geologists  before  it  was  understood  that  these 
two  elements  had  been  equally  active  in  building 
up  the  crust  of  the  earth.  The  ground  was  hotly 
contested  by  the  disciples  of  the  two  geological 
schools,  one  of  which  held  that  the  solid  envelope 
of  the  earth  was  exclusively  due  to  the  influence 
of  fire,  while  the  other  insisted  that  it  had  been 
accumulated  wholly  under  the  agency  of  water. 
This  difference  of  opinion  grew  up  very  natu- 
rally; for  the  great  leaders  of  the  two  schools 


AMERICA  THE   OLD   WORLD.  7 

lived  in  different  localities,  and  pursued  their 
investigations  over  regions  where  the  geological 
phenomena  were  of  an  entirely  opposite  char- 
acter, —  the  one  exhibiting  the  effect  of  volcanic 
eruptions,  the  other  that  of  stratified  deposits. 
It  was  the  old  story  of  the  two  knights  on  oppo- 
site sides  of  the  shield,  one  swearing  that  it  was 
made  of  gold,  the  other  that  it  was  made  of  sil- 
ver, and  almost  killing  each  other  before  they 
discovered  that  it  was  made  of  both.  So  prone 
are  men  to  hug  their  theories  and  shut  their  eyes 
to  any  antagonistic  facts,  that  it  is  related  of 
Werner,  the  great  leader  of  the  Aqueous  school, 
that  he  was  actually  on  his  way  to  see  a  geo- 
logical locality  of  especial  interest,  but,  being 
told  that  it  confirmed  the  views  of  his  opponents, 
he  turned  round  and  went  home  again,  refusing 
to  see  what  might  force  him  to  change  his  opin- 
ions. If  the -rocks  did  not  confirm  his  theory,  se 
much  the  worse  for  the  rocks,  —  he  would  none 
of  them.  At  last  it  was  found  that  the  two  great 
chemists,  fire  and  water,  had  worked  together  in 
the  vast  laboratory  of  the  globe,  and  since  then 
scientific  men  had  decided  to  work  together  also  ; 
and  if  they  still  have  a  passage  at  arms  occasion- 
ally over  some  doubtful  point,  yet  the  results  of 
their  investigations  are  ever  drawing  them  nearer 
to  each  other, —  since  men  who  study  truth, 
when  they  reach  their  goal,  must  always  meet  at 
last  on  common  ground. 


8  AMERICA  THE  OLD  WORLD. 

The  rocks  formed  under  the  influence  of  heat 
are  called,  in  geological  language,  the  Igneous, 
or,  as  some  naturalists  have  named  them,  the 
Plutonic  rocks,  alluding  to  their  fiery  origin, 
while  the  others  have  been  called  Aqueous  or 
Neptunic  rocks,  in  reference  to  their  origin  under 
the  agency  of  water.  A  simpler  term,  however, 
quite  as  distinctive,  and  more  descriptive  of  their 
structure,  is  that  of  the  stratified  and  massive  or 
unstratified  rocks.  We  shall  see  hereafter  how 
the  relative  position  of  these  two  classes  of  rocks 
and  their  action  upon  each  other  enable  us  to 
determine  the  chronology  of  the  earth,  to  com- 
pare the  age  of  her  mountains,  and,  if  we  have  no 
standard  by  which  to  estimate  the  positive  dura- 
tion of  her  continents,  to  say  at  least  which  was 
the  first-born  among  them,  and.  how  their  char- 
acteristic features  have  been  successively  worked 
out.  I  am  aware  that  many  of  these  inferences, 
drawn  from  what  is  called  "  the  geological  rec- 
ord," must  seem  to  be  the  work  of  the  imagina- 
tion. In  a  certain  sense  this  is  true,  —  for  imagi- 
nation, chastened  by  correct  observation,  is  our 
best  guide  in  the  study  of  Nature.  We  are  too 
apt  to  associate  the  exercise  of  this  faculty  with 
works  of  fiction,  while  it  is  in  fact  the  keenest 
detective  of  truth. 

Besides  the  stratified  and  massive  rocks,  there 
is  still  a  third  set,  produced  by  the  contact  of 


AMERICA  THE   OLD  WORLD.  9 

these  two,  and  called,  in  consequence  of  the 
changes  thus  brought  about,  the  Metamorphic 
rocks.  The  effect  of  heat  upon  clay  is  to  bake 
it  into  slate ;  limestone  under  the  influence  of 
heat  becomes  quick-lime,  or,  if  subjected  after- 
wards to  the  action  of  water,  it  is  changed  to 
mortar  ;  sand  under  the  same  agency  is  changed 
to  a  coarse  kind  of  glass.  Suppose,  then,  that 
a  volcanic  eruption  takes  place  in  a  region  of  the 
earth's  surface  where  successive  layers  of  lime- 
stone, of  clay,  and  of  sandstone  have  been  previ- 
ously deposited  by  the  action  of  water.  If  such 
an  eruption  has  force  enough  to  break  through 
these  beds,  the  hot,  melted  masses  will  pour  out 
through  the  rent,  flow  over  its  edges,  and  fill  all 
the  lesser  cracks  and  fissures  produced  by  such  a 
disturbance.  What  will  be  the  effect  upon  the 
stratified  rocks  ?  Wherever  these  liquid  masses, 
melted  by  a  heat  more  intense  than  can  be  pro- 
duced by  any  artificial  means,  have  flowed  over 
them  or  cooled  in  immediate  contact  with  them, 
the  clays  will  be  changed  to  slate,  the  limestone 
will  have  assumed  a  character  more  like  marble, 
while  the  sandstone  will  be  vitrified.  This  is 
exactly  what  has  been  found  to  be  the  case,  wher- 
ever the  stratified  rocks  have  been  penetrated  by 
the  melted  masses  from  beneath.  They  have 
been  themselves  partially  melted  by  the  contact, 
and  when  they  have  cooled  again,  their  stratifica- 
i* 


10  AMERICA  XtfE   OLD  WORLD. 

tion,  though  still  perceptible,  has  been  partly  ob- 
literated, and  their  substance  changed.  Such 
effects  may  often  be  traced  in  dikes,  which  are 
only  the  cracks  in  rocks  filled  by  materials  poured 
into  them  at  some  period  of  eruption  when  the 
melted  masses  within  the  earth  were  thrown  out 
and  flowed  like  water  into  any  inequality  or  de- 
pression of  the  surface  around.  The  walls  enclos- 
ing such  a  dike  are  often  found  to  be  completely 
altered  by  contact  with  its  burning  contents,  and 
to  have  assumed  a  character  quite  different  from 
the  rocks  of  which  they  make  a  part ;  while  the 
mass  itself  which  fills  the  fissure  shows  by  the 
character  of  its  crystallization  that  it  has  cooled 
more  quickly  on  the  outside,  where  it  meets  the 
walls,  than  at  the  centre. 

The  first  two  great  classes  of  rocks,  the  un- 
stratified  and  stratified  rocks,  represent  different 
epochs  in  the  world's  physical  history :  the  for- 
mer mark  its  revolutions,  while  the  latter  chron- 
icle its  periods  of  rest.  All  mountains  and  moun- 
tain-chains have  been  upheaved  by  great  convul- 
sions of  the  globe,  which  rent  asunder  the  surface 
of  the  earth,  destroyed  the  animals  and  plants 
living  upon  it  at  the  time,  and  were  then  suc- 
ceeded by  long  intervals  of  repose,  when  all 
things  returned  to  their  accustomed  order,  ocean 
and  river  deposited  fresh  beds  in  uninterrupted 
succession,  the  accumulation  of  materials  went 


AMERICA  THE   OLD  WORLD.  11 

on  as  before,  a  new  set  of  animals  and  plants 
were  introduced,  and  a  time  of  building  up  and 
renewing  followed  the  time  of  destruction.  These 
periods  of  revolution  are  naturally  more  difficult 
to  decipher  than  the  periods  of  rest ;  for  they 
have  so  torn  and  shattered  the  beds  they  up- 
lifted, disturbing  them  from  their  natural  rela- 
tions to  each  other,  that  it  is  not  easy  to  recon- 
struct the  parts  and  give  them  coherence  and 
completeness  again.  But  within  the  last  half- 
century  this  work  has  been  accomplished  in  many 
parts  of  the  world  with  an  amazing  degree  of 
accuracy,  considering  the  disconnected  character 
of  the  phenomena  to  be  studied ;  and  I  think  I 
shall  be  able  to  convince  my  readers  that  the 
modern  results  of  geological  investigation  are 
perfectly  sound  logical  inferences  from  well-estab- 
lished facts.  In  this,  as  in  so  many  other  things, 
we  are  but  "  children  of  a  larger  growth."  The 
world  is  the  geologist's  great  puzzle-box ;  he 
stands  before  it  like  the  child  to  whom  the  sepa- 
rate pieces  of  his  puzzle  remain  a  mystery  till  he 
detects  their  relation  and  sees  where  they  fit,  and 
then  his  fragments  grow  at  once  into  a  connected 
picture  beneath  his  hand. 

It  is  a  curious  fact  in  the  history  of  progress, 
that,  by  a  kind  of  intuitive  insight,  the  earlier 
observers  seem  to  have  had  a  wider,  more  com- 
prehensive recognition  of  natural  phenomena  as 


12  AMERICA  THE   OLD  WORLD. 

a  whole  than  their  successors,  who  far  excel 
them  in  their  knowledge  of  special  points,  but 
often  lose  their  grasp  of  broader  relations  in  the 
more  minute  investigation  of  details.  When  geo- 
logists first  turned  their  attention  to  the  physical 
history  of  the  earth,  they  saw  at  once  certain 
great  features  which  they  took  to  be  the  skeleton 
and  basis  of  the  whole  structure.  They  saw  the 
great  masses  of  granite  forming  the  mountains 
and  mountain-chains,  with  the  stratified  rocks 
resting  against  their  slopes ;  and  they  assumed 
that  granite  was  the  first  primary  agent,  and  that 
all  stratified  rocks  must  be  of  a  later  formation. 
Although  this  involved  a  partial  error,  as  we 
shall  see  hereafter,  when  we  trace  the  upheavals 
of  granite  even  into  comparatively  modern  peri- 
ods, yet  it  held  an  important  geological  truth 
also ;  for,  though  granite  formations  are  by  no 
means  limited  to  those  early  periods,  they  are 
nevertheless  very  characteristic  of  them,  and  are 
indeed  the  foundation-stones  on  which  the  phys- 
ical history  of  the  globe  is  built. 

Starting  from  this  landmark,  the  earlier  geol- 
ogists divided  the  world's  history  into  three  peri- 
ods. As  the  historian  recognizes  as  distinct 
phases  in  the  growth  of  the  human  race  Ancient 
History,  the  Middle  Ages,  and  Modern  History, 
so  they  distinguish  between  what  they  call  the 
Primary  period,  when,  as  they  believed,  no  life 


AMERICA  THE   OLD  WORLD.  13 

stirred  on  the  surface  of  the  earth ;  the  Secondary 
or  middle  period,  when  animals  and  plants  were 
introduced  and  the  land  began  to  assume  conti- 
nental proportions ;  and  the  Tertiary  period,  or 
comparatively  modern  geological  times,  when  the 
aspect  of  the  earth  as  well  as  its  inhabitants  was 
approaching  more  nearly  to  the  present  condition 
of  things.  But  as  their  investigations  proceeded, 
they  found  that  every  one  of  these  great  ages  of 
the  world's  history  was  divided  into  numerous 
lesser  epochs,  each  of  which  had  been  character- 
ized by  a  peculiar  set  of  animals  and  plants,  and 
had  been  closed  by  some  great  physical  convul- 
sion, disturbing  and  displacing  the  materials  ac- 
cumulated during  such  a  period  of  rest. 

The  further  study  of  these  subordinate  periods 
showed  that  what  had  been  called  Primary 'for- 
mations, the  volcanic  or  Plutonic  rocks,  formerly 
believed  to  be  confined  to  the  first  geological 
ages,  belonged  to  all  the  periods,  successive  erup- 
tions having  taken  place  at  all  times,  pouring 
up  through  the  accumulated  deposits,  penetrat- 
ing and  injecting  their  cracks,  fissures,  and  in- 
equalities, as  well  as  throwing  out  large  masses 
on  the  surface.  Up  to  our  own  day  there  has 
never  been  a  period  when  such  eruptions  have 
not  taken  place,  though  they  have  been  con- 
stantly diminishing  in  frequency  and  extent.  In 
consequence  of  this  discovery,  that  rocks  of  ig- 


14  AMEEICA  THE   OLD   WORLD. 

neons  character  were  by  no  means  exclusively 
characteristic  of  the  earliest  times,  they  are  now 
classified  together  upon  very  different  grounds 
from  those  on  which  geologists  first  united  them ; 
though,  as  the  name  Primary  was  long  retained, 
we  still  find  it  applied  to  them,  even  in  geo- 
logical works  of  quite  recent  date.  This  defect 
of  nomenclature  is  to  be  regretted,  as  likely  to 
mislead  the  student,  because  it  seems  to  refer  to 
time ;  whereas  it  no  longer  signifies  the  age  of 
the  rocks,  but  simply  their  character.  The  name 
Plutonic  or  Massive  rocks  is,  however,  now  al- 
most universally  substituted  for  that  of  Primary. 
A  wide  field  of  investigation  still  remains  to  be 
explored  by  the  chemist  and  the  geologist  to- 
gether, in  the  mineralogical  character  of  the 
Plutonic  rocks,  which  differs  greatly  in  the  dif- 
ferent periods.  The  earlier  eruptions  seem  to 
have  been  chiefly  granitic,  though  this  must  not 
be  understood  in  too  wide  a  sense,  since  there 
are  granite  formations  even  as  late  as  the  Terti- 
ary period;  those  of  the  middle  periods  were 
mostly  porphyries»and  basalts ;  while  in  the  more 
recent  ones,  lavas  predominate.  We  have  as  yet 
no  clue  to  the  laws  by  which  this  distribution  of 
volcanic  elements  in  the  formation  of  the  earth  is 
regulated ;  but  there  is  found  to  be  a  difference 
in  the  crystals  of  the  Plutonic  rocks  belonging 
to  different  ages,  which,  when  fully  understood, 


AMERICA  THE  OLD  WORLD.         15 

may  enable  us  to  determine  the  age  of  any  Phi- 
tonic  rock  by  its  mode  of  crystallization  ;  so  that 
the  mineralogist  will  as  readily  tell  you  by  its 
crystals  whether  a  bit  of  stone  of  igneous  origin 
belongs  to  this  or  that  period  of  the  world's  his- 
tory, as  the  palaeontologist  will  tell  you  by  its 
fossils  whether  a  piece  of  rock  of  aqueous  origin 
belongs  to  the  Silurian  or  Devonian  or  Carbon- 
iferous deposits. 

Although  subsequent  investigations  have  mul- 
tiplied so  extensively  not  only  the  number  of  geo- 
logical periods,  but  also  the  successive  creations 
that  have  characterized  them,  yet  the  first  gen- 
eral division  into  three  great  eras  was  neverthe- 
less founded  upon  a  broad  and  true  generaliza- 
tion. In  the  first  stratified  rocks  in  which  any 
organic  remains  are  found,  the  highest  animals 
are  fishes,  and  the  highest  plants  are  crypto- 
gams ;  in  the  middle  periods  reptiles  come  in, 
accompanied  by  fern  and  moss  forests ;  in  later 
times  quadrupeds  are  introduced,  with  a  dicoty- 
ledonous vegetation.  So  closely  does  the  march 
of  animal  and  vegetable  life  keop  pace  With  the 
material  progress  of  the  world,  that  we  may  well 
consider  these  three  divisions,  included  under 
the  first  general  classification  of  its  physical  his- 
tory, as  the  three  Ages  of  Nature ;  the  more  im- 
portant epochs  which  subdivide  them  may  be 
compared  to  so  many  great  dynasties,  while  the 


16         AMERICA  THE  OLD  WORLD. 

lesser  periods  are  the  separate  reigns  contained 
therein.  Of  such  epochs  there  are  ten,  well 
known  to  geologists ;  of  the  lesser  periods  about 
sixty  are  already  distinguished,  while  many  more 
loom  up  from  the  dim  regions  of  the  past,  just 
discerned  by  the  eye  of  science,  though  their  his- 
tory is  not  yet  unravelled. 

Before  proceeding  further,  I  will  enumerate 
the  geological  epochs  in  their  succession,  confin- 
ing myself,  however,  to  such  as  are  perfectly  well 
established,  without  alluding  to  those  of  which 
the  limits  are  less  definitely  determined,  and 
which  are  still  subject  to  doubts  and  discussions 
among  geologists.  As  I  do  not  propose  to  make 
here  any  treatise  of  Geology,  but  simply  to  place 
before  my  readers  some  pictures  of  the  old  world, 
with  the  animals  and  plants  that  have  inhabited 
it  at  various  times,  I  shall  avoid,  as  far  as  pos- 
sible, all  debatable  ground,  and  confine  myself  to 
those  parts  of  my  subject  which  are  best  known, 
and  can  therefore  be  more  clearly  presented. 

First,  we  have  the  Azoic  period,  devoid  of  life, 
as  its  name  signifies, — namely,  the  earliest  strati- 
fied deposits  upon  the  heated  film  forming  the 
first  solid  surface  of  the  earth,  in  which  no  trace 
of  living  thing  has  ever  been  found.  Next  comes 
the  Silurian  period,  when  the  crust  of  the  earth 
had  thickened  and  cooled  sufficiently  to  render 
the  existence  of  animals  and  plants  upon  it  pos- 


AMERICA  THE  OLD  WORLD.         17 

sible,  and  when  the  atmospheric  conditions  neces- 
sary to  their  maintenance  were  already  estab- 
lished. Many  of  the  names  given  to  these 
periods  are  by  no  means  significant  of  their  char- 
acter, but  are  merely  the  result  of  accident :  as, 
for  instance,  that  of  Silurian,  given  by  Sir  Rod- 
erick Murchison  to  this  set  of  beds,  because  he 
first  studied  them  in  that  part  of  Wales  occu- 
pied by  the  ancient  tribe  of  the  Silures.  The 
next  period,  the  Devonian,  was  for  a  similar  rea- 
son named  after  the  county  of  Devonshire,  in 
England,  where  it  was  first  investigated.  Upon 
this  follows  the  Carboniferous  period,  with  the 
immense  deposits  of  coal  from  which  it  derives 
its  name.  Then  comes  the  Permian  period, 
named,  again,  from  local  circumstances,  the  first 
investigation  of  its  deposits  having  taken  place  in 
the  province  of  Permia  in  Russia.  Next  in  suc- 
cession we  have  the  Triassic  period,  so  called 
from  the  trio  of  rocks,  the  red  sandstone,  Mus- 
chel  Kalk  (shell-limestone),  and  Keuper  (clay), 
most  frequently  combined  in  its  formations  ;  the 
Jurassic,  so  amply  illustrated  in  the  chain  of  the 
Jura,  where  geologists  first  found  the  clue  to  its 
history ;  and  the  Cretaceous  period,  to  which  the 
chalk  cliffs  of  England  and  all  the  extensive 
chalk  deposits  belong.  Upon  these  follow  the 
so-called  Tertiary  formations,  divided  into  three 
periods,  all  of  which  have  received  most  char- 


18         AMERICA  THE  OLD  WORLD. 

acteristic  names.  In  this  epoch  of  the  world's 
history  we  see  the  first  approach  to  a  condition 
of  things  resembling  that  now  prevailing,  and  Sir 
Charles  Lyell  has  most  fitly  named  its  three 
divisions,  the  Eocene,  Miocene,  and  Pliocene. 
The  termination  of  the  three  words  is  made  from 
the  Greek  word  Kainos,  recent ;  while  Eos  sig- 
nifies dawn,  Melon  less,  and  Pleion  more.  Thus 
Eocene  indicates  the  dawn  of  recent  species,  Pli- 
ocene their  increase,  while  Miocene,  the  inter- 
mediate term,  means  less  recent.  Above  these 
deposits  comes  what  has  been  called  in  science 
the  present  period,  —  the  modern  times  of  the 
geologist,  —  that  period  to  which  man  himself  be- 
longs, and  since  the  beginning  of  which,  though 
its  duration  be  counted  by  hundreds  of  thousands 
of  years,  there  has  been  no  alteration  in  the  gen- 
eral configuration  of  the  earth,  consequently  no 
important  modification  of  its  climatic  conditions, 
and  no  change  in  the  animals  and  plants  inhabit- 
ing it. 

I  have  spoken  of  the  first  of  these  periods,  the 
Azoic,  as  having  been  absolutely  devoid  of  life, 
and  I  believe  this  statement  to  be  strictly  true  ; 
but  I  ought  to  add  that  there  is  a  difference  of 
opinion  among  geologists  upon  this  point,  many 
believing  that  the  first  surface  of  our  globe  may 
have  been  inhabited  by  living  beings,  but  that  all 
traces  of  their  existence  have  been  obliterated  by 


AMERICA   THE   OLD   WORLD.  19 

the  eruptions  of  melted  materials,  which  not  only 
altered  the  character  of  those  earliest  stratified 
rocks,  but  destroyed  all  the  organic  remains  con- 
tained in  them.  It  will  be  my  object  to  show  in 
this  series  of  papers,  not  only  that  the  absence 
of  the  climatic  and  atmospheric  conditions  essen- 
tial to  organic  life,  as  we  understand  it,  must 
have  rendered  the  previous  existence  of  any  liv- 
ing beings  impossible,  but  also  that  the  complete- 
ness of  the  Animal  Kingdom  in  those  deposits 
where  we  first  find  organic  remains,  its  intelli- 
gible and  coherent  connection  with  the  succes- 
sive creations  of  all  geological  times  and  with  the 
animals  now  living,  afford  the  strongest  internal 
evidence  that  we  have  indeed  found  in  the  lower 
Silurian  formations,  immediately  following  the 
Azoic,  the  beginning  of  life  upon  earth.  When 
a  story  seems  to  us  complete  and  consistent  from 
the  beginning  to  the  end,  we  shall  not  seek  for  a 
first  chapter,  even  though  the  copy  in  which  we 
have  read  it  be  so  torn  and  defaced  as  to  suggest 
the  idea  that  some  portion  of  it  may  have  been 
lost.  The  unity  of  the  work,  as  a  whole,  is  an 
incontestable  proof  that  we  possess  it  in  its  origi- 
nal integrity.  The  validity  of  this  argument  will 
be  recognized,  perhaps,  only  by  those  naturalists 
to  whom  the  Animal  Kingdom  has  begun  to 
appear  as  a  connected  whole.  For  those  who  do 
not  see  order  in  Nature  it  can  have  no  value. 


20  AMERICA  THE   OLD  WORLD. 

For  a  table  containing  the  geological  periods 
in  their  succession,  I  would  refer  to  any  modern 
text-book  of  Geology,  or  to  an  article  in  the  "  At- 
lantic Monthly  "  for  March,  1862,  upon  «  Meth- 
ods of  Study  in  Natural  History,"  where  they 
are  given  in  connection  with  the  order  of  intro- 
duction of  animals  upon  earth. 

Were  these  sets  of  rocks  found  always  in  the 
regular  sequence  in  which  I  have  enumerated 
them,  their  relative  age  would  be  easily  deter- 
mined, for  their  superposition  would  tell  the 
whole  story:  the  lowest  would,  of  course,  be  the 
oldest,  and  we  might  follow  without  difficulty 
the  ascending  series,  till  we  reached  the  youngest 
and  uppermost  deposits.  But  their  succession 
has  been  broken  up  by  frequent  and  violent  al- 
terations in  the  configuration  of  the  globe.  Land 
and  water  have  changed  their  level,  —  islands 
have  been  transformed  to  continents,  —  sea-bot- 
toms have  become  dry  land,  and  dry  land  has 
sunk  to  form  sea-bottom,  —  Alps  and  Himalayas, 
Pyrenees  and  Apennines,  Alleghanies  and  Rocky 
Mountains,  have  had  their  stormy  birthdays  since 
many  of  these  beds  have  been  piled  one  above 
another,  and  there  are  but  few  spots  on  the  earth's 
surface  where  any  number  of  them  may  be  found 
in  their  original  order  and  natural  position. 
When  we  remember  that  Europe,  which  lies 
before  us  on  the  map  as  a  continent,  was  once 


AMERICA  THE   OLD  WORLD.  21 

an  archipelago  of  islands,  —  that,  where  the  Pyr- 
enees raised  their  rocky  barrier  between  France 
and  Spain,  the  waters  of  the  Mediterranean  and 
Atlantic  met,  —  that,  where  the  British  Channel 
flows,  dry  land  united  England  and  France,  and 
Nature  in  those  days  made  one  country  of  the 
lands  parted  since  by  enmities  deeper  than  the 
waters  that  run  between,  —  when  we  remember, 
in  short,  all  the  fearful  convulsions  that  have 
torn  asunder  the  surface  of  the  earth,  as  if  her 
rocky  record  had  indeed  been  written  on  paper, 
we  shall  find  a  new  evidence  of  the  intellectual 
unity  which  holds  together  the  whole  physical 
history  of  the  globe  in  the  fact  that  through  all 
the  storms  of  time  the  investigator  is  able  to 
trace  one  unbroken  thread  of  thought  from  the 
beginning  to  the  present  hour. 

The  tree  is  known  by  its  fruits,  —  and  the 
fruits  of  chance  are  incoherence,  incompleteness, 
unsteadiness,  the  stammering  utterance  of  blind, 
unreasoning  force.  A  coherence  that  binds  all 
the  geological  ages  in  one  chain,  a  stability  of 
purpose  that  completes  in  the  beings  born  to-day 
an  intention  expressed  in  the  first  creatures  that 
swam  in  the  Silurian  ocean  or  crept  upon  its 
shores,  a  steadfastness  of  thought,  practically 
recognized  by  man,  if  not  acknowledged  by  him, 
whenever  he  traces  the  intelligent  connection  be- 
tween the  facts  of  Nature  and  combines  them 


22         AMERICA  THE  OLD  WORLD. 

into  what  he  is  pleased  to  call  his  system  of  Ge- 
ology, or  Zoology,  or  Botany,  —  these  things  are 
not  the  fruits  of  chance  or  of  an  unreasoning 
force,  but  the  legitimate  results  of  intellectual 
power.  There  is  a  singular  lack  of  logic,  as  it 
seems  to  me,  in  the  views  of  the  materialistic 
naturalists.  While  they  consider  classification, 
or,  in  other  words,  their  expression  of  the  rela- 
tions between  animals  or  between  physical  facts 
of  any  kind,  as  the  work  of  their  intelligence, 
they  believe  the  relations  themselves  to  be  the 
work  of  physical  causes.  The  more  direct  in- 
ference surely  is,  that,  if  it  requires  an  intelligent 
mind  to  recognize  them,  it  must  have  required 
an  intelligent  mind  to  establish  them.  These 
relations  existed  before  man  was  created  ;  they 
have  existed  ever  since  the  beginning  of  time ; 
hence,  what  we  call  the  classification  of  facts  is 
not  the  work  of  his  mind  in  any  direct  original 
sense,  but  the  recognition  of  an  intelligent  action 
prior  to  his  own  existence. 

There  is,  perhaps,  no  part  of  the  world,  cer- 
tainly none  familiar  to  science,  where  the  early 
geological  periods  can  be  studied  with  so  much 
ease  and  precision  as  in  the  United  States.  Along 
their  northern  borders,  between  Canada  and  the 
United  States,  there  runs  the  low  line  of  hills 
known  as  the  Laurentian  Hills.  Insignificant  in 
height,  nowhere  rising  more  than  fifteen  hundred 


AMEKICA  THE  OLD  WORLD.         23 

or  two  thousand  feet  above  the  level  of  the  sea, 
these  are  nevertheless  the  first  mountains  that 
broke  the  uniform  level  of  the  earth's  surface  and 
lifted  themselves  above  the  waters.  Their  low 
stature,  as  compared  with  that  of  other  more  lofty 
mountain-ranges,  is  in  accordance  with  an  in- 
variable rule,  by  which  the  relative  age  of  moun- 
tains may  be  estimated.  The  oldest  mountains 
are  the  lowest,  while  the  younger  and  more  re- 
cent ones  tower  above  their  elders,  and  are  usu- 
ally more  torn  and  dislocated  also.  This  is  easily 
understood,  when  we  remember  that  all  moun- 
tains and  mountain-chains  are  the  result  of  up- 
heavals, and  that  the  violence  of  the  outbreak 
must  have  been  in  proportion  to  the  strength  of 
the  resistance.  When  the  crust  of  the  oarth  was 
so  thin  that  the  heated  masses  within  easily  broke 
through  it,  they  were  not  thrown  to  so  great  a 
height,  and  formed  comparatively  low  elevations, 
such  as  the  Canadian  hills  or  the  mountains  of 
Bretagne  and  Wales.  But  in  later  times,  when 
young,  vigorous  giants,  such  as  the  Alps,  the 
Himalayas,  or,  later  still,  the  Rocky  Mountains, 
forced  their  way  out  from  their  fiery  prison- 
house,  the  crust  of  the  earth  was  much  thicker, 
and  fearful  indeed  must  have  been  the  convul- 
sions which  attended  their  exit. 

The  Laurentian  Hills   form,  then,  a  granite 
range,  stretching  from  Eastern  Canada  to  the 


24  AMERICA  THE  OLD  WORLD. 

Upper  Mississippi,  and  immediately  along  its  base 
are  gathered  the  Azoic  deposits,  the  first  strati- 
fied beds,  in  which  the  absence  of  life  need  not 
surprise  us,  since  they  were  formed  beneath  a 
heated  ocean.  As  well  might  we  expect  to  find 
the  remains  of  fish  or  shells  or  crabs  at  the  bot- 
tom of  geysers  or  of  boiling  springs,  as  on  those 
early  shores  bathed  by  an  ocean  of  which  the 
heat  must  have  been  so  intense.  Although,  from 
the  condition  in  which  we  find  it,  this  first  granite 
range  has  evidently  ,never  been  disturbed  by  any 
violent  convulsion  since  its  first  upheaval,  yet 
there  has  been  a  gradual  rising  of  that  part  of 
the  continent,  for  the  Azoic  beds  do  not  lie  hori- 
zontally along  the  base  of  the  Laurentian  Hills 
in  the  position  in  which  they  must  originally 
have  been  deposited,  but  are  lifted  and  rest 
against  their  slopes.  They  have  been  more  or 
less  dislocated  in  this  process,  and  are  greatly 
metamorphized  by  the  intense  heat  to  which  they 
must  have  been  exposed.  Indeed,  all  the  oldest 
stratified  rocks  have  been  baked  by  the  prolonged 
action  of  heat. 

It  may  be  asked  how  the  materials  for  those 
first  stratified  deposits  were  provided.  In  later 
times,  when  an  abundant  and  various  soil  covered 
the  earth,  when  every  river  brought  down  to  the 
ocean,  not  only  its  yearly  tribute  of  mud  or  clay 
or  lime,  but  the  debris  of  animals  and  plants  that 


AMERICA  THE  OLD  WORLD.         25 

lived  and  died  in  its  waters  or  along  its  banks, 
when  every  lake  and  pond  deposited  at  its  bot- 
tom in  successive  layers  the  lighter  or  heavier 
materials  floating  in  its  waters  and  settling  grad- 
ually beneath  them,  the  process  by  which  strati- 
fied materials  are  collected  and  gradually  harden 
into  rock  is  more  easily  understood.  But  when 
the  solid  surface  of  the  earth  was  only  just  begin- 
ning to  form,  it  would  seem  that  the  floating 
matter  in  the  sea  can  hardly  have  been  in  suf- 
ficient quantity  to  form  any  extensive  deposits. 
No  doubt  there  was  some  abrasion  even  of  that 
first  crust ;  but  the  more  abundant  source  of  the 
earliest  stratification  is  to  be  found  in  the  sub- 
marine volcanoes  that  poured  their  liquid  streams 
into  the  first  ocean.  At  what  rate  these  materi- 
als would  be  distributed  and  precipitated  in  reg- 
ular strata  it  is  impossible  to  determine  ;  but  that 
volcanic  materials  were  so  deposited  in  layers  is 
evident  from  the  relative  position  of  the  earliest 
rocks.  I  have  already  spoken  of  the  innumer- 
able chimneys  perforating  the  Azoic  beds,  narrow 
outlets  of  Plutonic  rock,  protruding  through  the 
earliest  strata.  Not  only  are  such  funnels  filled 
with  the  crystalline  mass  of  granite  that  flowed 
through  them  in  a  liquid  state,  but  it  has  often 
poured  over  their  sides,  mingling  with  the  strati- 
fied beds  around.  In  the  present  state  of  our 
knowledge,  we  can  explain  such  appearances  only 


26         AMERICA  THE  OLD  WORLD. 

by  supposing  that  the  heated  materials  within 
the  earth's  crust  poured  out  frequently,  meeting 
little  resistance,  —  that  they  then  scattered  and 
were  precipitated  in  the  ocean  around,  settling 
in  successive  strata  at  its  bottom,  —  that  through 
such  strata  the  heated  masses  within  continued 
to  pour  again  and  again,  forming  for  themselves 
the  chimney-like  outlets  above  mentioned. 

Such,  then,  was  the  earliest  American  land,  — 
a  long,  narrow  island,  almost  continental  in  its 
proportions,  since  it  stretched  from  the  eastern 
borders  of  Canada  nearly  to  the  point  where  now 
the  base  of  the  Rocky  Mountains  meets  the  plain 
of  the  Mississippi  Valley.  We  may  still  walk 
along  its  ridge  and  know  that  we  tread  upon  the 
ancient  granite  that  first  divided  the  waters  into 
a  northern  and  southern  ocean ;  and  if  our  im- 
aginations will  carry  us  so  far,  we  may  look  down 
toward  its  base  and  fancy  how  the  sea  washed 
against  this  earliest  shore  of  a  lifeless  world. 
This  is  no  romance,  but  the  bald,  simple  truth ; 
for  the  fact  that  this  granite  band  was  lifted  out 
of  the  waters  so  early  in  the  history  of  the  world, 
and  has  not  since  been  submerged,  has,  of  course, 
prevented  any  subsequent  deposits  from  forming 
above  it.  And  this  is  true  of  all  the  northern 
part  of  the  United  States.  It  has  been  lifted 
gradually,  the  bods  deposited  in  one  period  being 
subsequently  raised,  and  forming  a  shore  along 


AMEKICA  THE   OLD  WORLD.  27 

which  those  of  the  succeeding  one  collected,  so 
that  we  have  their  whole  sequence  before  us.  In 
regions  where  all  the  geological  deposits,  Silu- 
rian, Devonian,  Carboniferous,  Permian,  Trias- 
sic,  etc.,  are  piled  one  upon  another,  and  we  can 
get  a  glimpse  of  their  internal  relations  only 
where  some  rent  has  laid  them  open,  or  where 
their  ragged  edges,  worn  away  by  the  abrad- 
ing action  of  external  influences,  expose  to  view 
their  successive  layers,  it  must,  of  course,  be 
more  difficult  to  follow  their  connection.  For 
this  reason  the  American  continent  offers  facil- 
ities to  the  geologist  denied  to  him  in  the  so- 
called  Old  World,  where  the  earlier  deposits  are 
comparatively  hidden,  and  the  broken  character 
of  the  land,  intersected  by  mountains  in  every 
direction,  renders  his  investigation  still  more  dif- 
ficult. Of  course,  when  I  speak  of  the  geological 
deposits  as  so  completely  unveiled  to  us  here,  I 
do  not  forget  the  sheet  of  drift  which  covers  the 
continent  from  North  to  South,  and  which  we 
shall  discuss  hereafter,  when  I  reach  that  part  of 
my  subject.  But  the  drift  is  only  a  superficial 
and  recent  addition  to  the  soil,  resting  loosely 
above  the  other  geological  deposits,  and  arising, 
as  we  shall  see,  from  very  different  causes. 

In  this  article  I  have  intended  to  limit  myself 
to  a  general  sketch  of  the  formation  of  the  Lau- 
rentian  Hills  with  the  Azoic  stratified  beds  rest 


28  AMERICA  THE   OLD   WORLD. 

ing  against  them.  In  the  Silurian  epoch  follow- 
ing the  Azoic  we  have  the  first  beach  on  which, 
any  life  stirred;  it  extended  along  the  base  of 
the  Azoic  beds,  widening  by  its  extensive  de- 
posits the  narrow  strip  of  land  already  upheaved. 
I  propose  in  my  next  article  to  invite  my  readers 
to  a  stroll  with  me  along  that  beach. 


II. 

THE   SILURIAN  BEACH. 

WITH  what  interest  do  we  look  upon  any 
relic  of  early  human  history !  The  monu- 
ment that  tells  of  a  civilization  whose  hieroglyphic 
records  we  cannot  even  decipher,  the  slightest 
trace  of  a  nation  that  vanished  and  left  no  sign 
of  its  life  except  the  rough  tools  and  utensils  bu- 
ried in  the  old  site  of  its  towns  or  villages,  arouses 
our  imagination  and  excites  our  curiosity.  Men 
gaze  with  awe  at  the  inscription  on  an  ancient 
Egyptian  or  Assyrian  stone  ;  they  hold  with  rev- 
erential touch  the  yellow  parchment-roll  whose 
dim,  defaced  characters  record  the  meagre  learn- 
ing of  a  buried  nationality ;  and  the  announce- 
ment, that  for  centuries  the  tropical  forests  of 
Central  America  have  hidden  within  their  tan- 
gled growth  the  ruined  homes  and  temples  of  a 
past  race,  stirs  the  civilized  world  with  a  strange, 
deep  wonder. 

To  me  it  seems,  that  to  look  on  the  first  land 
that  was  ever  lifted  above  the  waste  of  waters,  to 
follow  the  shore  where  the  earliest  animals  and 


30  THE  SILUEIAN  BEACH. 

plants  were  created  when  the  thought  of  God  first 
expressed  itself  in  organic  forms,  to  hold  in  one's 
hand  a  bit  of  stone  from  an  old  sea-beach,  hard- 
ened into  rock  thousands  of  centuries  ago,  and 
studded  with  the  beings  that  once  crept  upon  its 
surface  or  were  stranded  there  by  some  retreating 
wave,  is  even  of  deeper  interest  to  men  than  the 
relics  of  their  own  race,  for  these  things  tell  more 
directly  of  the  thoughts  and  creative  acts  of  God. 

Standing  in  the  neighborhood  of  Whitehall, 
near  Lake  George,  one  may  look  along  such  a 
sea-shore,  and  see  it  stretching  westward  and 
sloping  gently  southward  as  far  as  the  eye  can 
reach.  It  must  have  had  a  very  gradual  slope, 
and  the  waters  must  have  been  very  shallow  ; 
for  at  that  time  no  great  mountains  had  been  up- 
lifted, and  deep  oceans  are  always  the  concomi- 
tants of  lofty  heights.  We  do  not,  however, 
judge  of  this  by  inference  merely ;  we  have  an 
evidence  of  the  shallowness  of  the  sea  in  those 
days  in  the  character  of  the  shells  found  in  the 
Silurian  deposits,  which  shows  that  they  belonged 
in  shoal  waters. 

Indeed,  the  fossil  remains  of  all  times  tell  us 
almost  as  much  of  the  physical  condition  of  the 
world  at  different  epochs  as  they  do  of  its  animal 
and  vegetable  population.  When  Robinson  Cru- 
soe first  caught  sight  of  the  footprint  on  the  sand, 
he  saw  in  it  more  than  the  mere  footprint,  for  it 


THE  SILUEIAN  BEACH.  31 

spoke  to  him  of  the  presence  of  men  on  his  desert 
island.  We  walk  on  the  old  geological  shores, 
Like  Crusoe  along  his  beach,  and  the  footprints 
we  find  there  tell  us,  too,  more  than  we  actually 
see  in  them.  The  crust  of  our  earth  is  a  great 
cemetery,  where  the  rocks  are  tombstones  on 
which  the  buried  dead  have  written  their  own 
epitaphs.  They  tell  us  not  only  who  they  were 
and  when  and  where  they  lived,  but  much  also  of 
the  circumstances  under  which  they  lived.  We 
ascertain  the  prevalence  of  certain  physical  condi- 
tions at  special  epochs  by  the  presence  of  animals 
and  plants  whose  existence  and  maintenance  re- 
quired such  a  state  of  things,  more  than  by  any 
positive  knowledge  respecting  it.  Where  we  find 
the  remains  of  quadrupeds  corresponding  to  our 
ruminating  animals,  we  infer  not  only  land,  but 
grassy  meadows  also,  and  an  extensive  vegeta- 
tion ;  where  we  find  none  but  marine  animals, 
we  know  the  ocean  must  have  covered  the  earth  ; 
the  remains  of  large  reptiles,  representing,  though 
in  gigantic  size,  the  half  aquatic,  half  terrestrial 
reptiles  of  our  own  period,  indicate  to  us  the  ex- 
istence of  spreading  marshes  still  soaked  by  the 
retreating  waters ;  while  the  traces  of  such  ani- 
mals as  live  now  in  sand  and  shoal  waters,  or  in 
mud,  speak  to  us  of  shelving  sandy  beaches  and 
of  mud-flats.  The  eye  of  the  Trilobite  tells  us 
that  the  sun  shone  on  the  old  beach  where  he 


32  THE  SILURIAN  BEACH. 

lived ;  for  there  is  nothing  in  nature  without  a 
purpose,  and  when  so  complicated  an  organ  was 
made  to  receive  the  light,  there  must  have  been 
light  to  enter  it.  The  immense  vegetable  deposits 
in  the  Carboniferous  period  announce  the  intro- 
duction of  an  extensive  terrestrial  vegetation  ; 
and  the  impressions  left  by  the  wood  and  leaves 
of  the  trees  show  that  these  first  forests  must  have 
grown  in  a  damp  soil  and  a  moist  atmosphere. 
In  short,  all  the  remains  of  animals  and  plants 
hidden  in  the  rocks  have  something  to  tell  of  the 
climatic  conditions  and  the  general  circumstances 
under  which  they  lived,  and  the  study  of  fossils  is 
to  the  naturalist  a  thermometer  by  which  he  reads 
the  variations  of  temperature  in  past  times,  a 
plummet  by  which  he  sounds  the  depths  of  the 
ancient  oceans, —  a  register,  in  fact,  of  all  the  im- 
portant physical  changes  the  earth  has  undergone. 
But  although  the  animals  of  the  early  geologi- 
cal deposits  indicate  shallow  seas  by  their  simi- 
larity to  our  shoal-water  animals,  it  must  not  be 
supposed  that  they  are  by  any  means  the  same. 
On  the  contrary,  the  old  shells,  Crustacea,  corals, 
etc.,  represent  types  which  have  existed  in  all 
times  with  the  same  essential  structural  elements, 
but  under  different  specific  forms  in  the  several 
geological  periods.  And  here  it  may  not  be  amiss 
to  say  something  of  what  are  called  by  naturalists 
representative  types. 


THE  SILUEIAN  BEACH.  33 

The  statement  that  different  sets  of  animals 
and  plants  have  characterized  the  successive 
epochs  is  often  understood  as  indicating  a  dif- 
ference of  another  kind  than  that  which  distin- 
guishes animals  now  living  in  different  parts  of 
the  world.  This  is  a  mistake.  They  are  so- 
called  representative  types  all  over  the  globe, 
united  to  each  other  by  structural  relations  and 
separated  by  specific  differences  of  the  same  kind 
as  those  that  unite  and  separate  animals  of  differ- 
ent geological  periods.  Take,  for  instance,  mud- 
flats or  sandy  shores  in  the  same  latitudes  of 
Europe  and  America ;  we  find  living  on  each  ani- 
mals of  the  same  structural  character  and  of  the 
same  general  appearance,  but  with  certain  specific 
differences,  as  of  color,  size,  external  appendages, 
etc.  They  represent  each  other  on  the  two  conti- 
nents. The  American  wolves,  foxes,  bears,  rab- 
bits, are  not  the  same  as  the  European,  but  those 
of  one  continent  are  as  true  to  their  respective 
types  as  those  of  the  other;  under  a  somewhat 
different  aspect  they  represent  the  same  groups 
of  animals.  In  certain  latitudes,  or  under  condi- 
tions of  nearer  proximity,  these  differences  may 
be  less  marked.  It  is  well  known  that  there  is  a 
great  monotony  of  type,  not  only  among  animals 
and  plants,  but  in  the  human  races  also,  through- 
out the  Arctic  regions  ;  and  some  animals  charac- 
teristic of  the  high  North  reappear  under  such 
2*  c 


34  THE   SILUEIAN  BEACH. 

identical  forms  in  the  neighborhood  of  the  snow- 
fields  in  lofty  mountains,  that  to  trace  the  differ- 
ence between  the  ptarmigans,  rabbits,  and  other 
gnawing  animals  of  the  Alps,  for  instance,  and 
those  of  the  Arctics,  is  among  the  most  difficult 
problems  of  modern  science. 

And  so  is  it  also  with  the  animated  world  of 
past  ages  ;  in  similar  deposits  of  sand,  mud,  or 
lime,  in  adjoining  regions  of  the  same  geological 
age,  identical  remains  of  animals  and  plants  may 
be  found ;  while  at  greater  distances,  but  under 
similar  circumstances,  representative  species  may 
occur.  In  very  remote  regions,  however,  whether 
the  circumstances  be  similar  or  dissimilar,  the 
general  aspect  of  the  organic  world  differs  greatly, 
remoteness  in  space  being  thus  in  some  measure 
an  indication  of  the  degree  of  affinity  between  dif- 
ferent faunae.  In  deposits  of  different  geological 
periods  immediately  following  each  other,  we 
sometimes  find  remains  of  animals  and  plants  so 
closely  allied  to  those  of  earlier  or  later  periods 
that  at  first  sight  the  specific  differences  are 
hardly  discernible.  The  difficulty  of  solving 
these  questions,  and  of  appreciating  correctly  the 
differences  and  similarities  between  such  closely 
allied  organisms,  explains  the  antagonistic  views 
of  many  naturalists  respecting  the  range  of  exist- 
ence of  animals,  during  longer  or  shorter  geologi- 
cal periods ;  and  the  superficial  way  in  which  dis 


THE  SILURIAN  BEACH.  35 

cussions  concerning  the  transition  of  species  are 
carried  on,  is  mainly  owing  to  an  ignorance  of  the 
conditions  above  alluded  to.  My  own  personal 
observation  and  experience  in  these  matters  have 
led  me  to  the  conviction  that  every  geological 
period  has  had  its  own  representatives,  and  that 
no  single  species  has  been  repeated  in  successive 


The  laws  regulating  the  geographical  distribu- 
tion of  animals,  and  their  combination  into  dis- 
tinct zoological  provinces  called  faunae,  with  defi- 
nite limits,  are  very  imperfectly  understood  as 
yet ;  but  so  closely  are  all  things  linked  together 
from  the  beginning  till  to-day  that  I  am  con- 
vinced we  shall  never  find  the  clew  to  their 
meaning  till  we  carry  on  our  investigations  in 
the  past  and  the  present  simultaneously.  The 
same  principle  according  to  which  animal  and 
vegetable  life  is  distributed  over  the  surface  of 
the  earth  now,  prevailed  in  the  earliest  geological 
periods.  The  geological  deposits  of  all  times 
have  had  their  characteristic  faunae  under  vari- 
ous zones,  their  zoological  provinces  presenting 
special  combinations  of  animal  and  vegetable  life 
over  certain  regions,  and  their  representative 
types  reproducing  in  different  countries,  but  un- 
der similar  latitudes,  the  same  groups  with  spe- 
cific differences. 

Of  course,  the  nearer  we  approach  the  begin- 


36  THE   SILUKIAN  BEACH. 

ning  of  organic  life,  the  less  marked  do  we  find 
the  differences  to  be,  and  for  a  very  obvious  rea- 
son. The  inequalities  of  the  earth's  surface,  her 
mountain-barriers  protecting  whole  continents 
from  the  Arctic  winds,  her  open  plains  exposing 
others  to  the  full  force  of  the  polar  blasts,  her 
snug  valleys  and  her  lofty  heights,  her  table- 
lands and  rolling  prairies,  her  river-systems  and 
her  dry  deserts,  her  cold  ocean-currents  pouring 
down  from  the  high  North  on  some  of  her  shores, 
while  warm  ones  from  tropical  seas  carry  their 
softer  influence  to  others,  —  in  short,  all  the  con- 
trasts in  the  external  configuration  of  the  globe, 
with  the  physical  conditions  attendant  upon 
them,  are  naturally  accompanied  by  a  corre- 
sponding variety  in  animal  and  vegetable  life. 

But  in  the  Silurian  age,  when  there  were  no 
elevations  higher  than  the  Canadian  hills,  when 
water  covered  the  face  of  the  earth,  with  the  ex- 
ception of  a  few  isolated  portions  lifted  above  the 
almost  universal  ocean,  how  monotonous  must 
have  been  the  conditions  of  life !  And  what 
should  we  expect  to  find  on  those  first  shores  ? 
If  we  are  walking  on  a  sea-beach  to-day,  we  do 
not  look  for  animals  that  haunt  the  forests  or  roam 
over  the  open  plains,  or  for  those  that  live  in  shel- 
tered valleys  or  in  inland  regions  or  on  mountain- 
heights.  We  look  for  Shells,  for  Mussels  and 
Barnacles,  for  Crabs,  for  Shrimps,  for  Marine 


THE   SILUKIAN  BEACH.  37 

Worms,  for  Star-Fishes  and  Sea-Urchins,  and  we 
may  find  here  and  there  a  fish  stranded  on  the 
sand  or  tangled  in  the  sea-weed.  Let  us  remem- 
ber, then,  that,  in  the  Silurian  period,  the  world, 
so  far  as  it  was  raised  above  the  ocean,  was  a 
beach,  and  let  us  seek  there  for  such  creatures  as 
God  has  made  to  live  on  sea-shores,  and  not  be- 
little the  Creative  work,  or  say  that  He  first  scat- 
tered the  seeds  of  life  in  meagre  or  stinted  meas- 
ure, because  we  do  not  find  air-breathing  animals 
when  there  was  no  fitting  atmosphere  to  feed 
their  lungs,  insects  with  no  terrestrial  plants  to 
live  upon,  reptiles  without  marshes,  birds  with- 
out trees,  cattle  without  grass,  all  things,  in 
short,  without  the  essential  conditions  for  their 
existence. 

What  we  do  find,  —  and  these,  as  I  shall  en- 
deavor to  show  my  readers,  in  such  profusion 
that  it  would  seem  as  if  God,  in  the  joy  of  crea- 
tion, had  compensated  Himself  for  a  less  variety 
of  forms  in  the  greater  richness  of  the  early 
types,  —  is  an  immense  number  of  beings  belong- 
ing to  the  four  primary  divisions  of  the  Animal 
Kingdom,  but  only  to  those  classes  whose  repre- 
sentatives are  marine,  whose  home  then,  as  now 
was  either  in  the  sea  or  along  its  shores.  In 
other  words,  the  first  organic  creation  expressed 
in  its  totality  the  structural  conception  since 
carried  out  in  such  wonderful  variety  of  details, 


38  THE  SILURIAN  BEACH. 

and  purposely  limited  then,  because  the  world, 
which  was  to  be  the  home  of  the  higher  animals, 
was  not  yet  made  ready  to  receive  them. 

I  am  fully  aware  that  the  intimate  relations 
between  the  organic  and  physical  world  are  inter- 
preted by  many  as  indicating  the  absence,  rather 
than  the  presence,  of  an  intelligent  Creator. 
They  argue,  that  the  dependence  of  animals  on 
material  laws  gives  us  the  clew  to  their  origin  as 
well  as  to  their  maintenance.  Were  this  influ- 
ence as  absolute  and  unvarying  as  the  purely 
mechanical  action  of  physical  circumstances 
must  necessarily  be,  this  inference  might  have 
some  pretence  to  logical  probability,  —  though  it 
seems  to  me  unnecessary,  under  any  circumstan- 
ces, to  resort  to  climatic  influences  or  the  action 
of  any  physical  laws  to  explain  the  thoughtful 
distribution  of  the  organic  and  inorganic  world, 
so  evidently  intended  to  secure  for  all  beings 
what  best  suits  their  nature  and  their  needs. 
But  the  truth  is,  that,  while  these  harmonious 
relations  underlie  the^whole  creation  in  such  a 
manner  as  to  indicate  a  great  central  plan,  of 
which  all  things  are  a  part,  there  is  at  the  same 
time  a  freedom,  an  arbitrary  element  in  the 
mode  of  carrying  it  out,  which  seems  to  point  to 
the  exercise  of  an  individual  will ;  for,  side  by 
side  with  facts,  apparently  the  direct  result  of 
physical  laws,  are  other  facts,  the  nature  of 


THE  SILURIAN  BEACH.  39 

which  shows  a  complete  independence  of  exter- 
nal influences. 

Take,  for  instance,  the  similarity  ahove  alluded 
to  between  the  faunae  of  the  Arctics  and  that  of 
the  Alps,  certainly  showing  a  direct  relation  be- 
tween climatic  conditions  and  animal  and  vege- 
table life.  Yet  even  there,  where  the  shades  of 
specific  difference  between  many  animals  and 
plants  of  the  same  class  are  so  slight  as  to  baffle 
the  keenest  investigators,  we  have  representative 
types  both  in  the  Animal  and  Vegetable  King- 
doms as  distinct  and  peculiar  as  those  of  widely 
removed  and  strongly  contrasted  climatic  condi- 
tions. Shall  we  attribute  the  similarities  and 
the  differences  alike  to  physical  causes?  Com- 
pare, for  example,  the  Reindeer  of  the  Arctics 
with  the  Ibex  and  the  Chamois,  representing  the 
same  group  in  the  Alps.  Even  on  mountain- 
heights  of  similar  altitudes,  where  not  only  cli- 
mate, but  other  physical  conditions  would  sug- 
gest a  recurrence  of  identical  animals,  we  do  not 
find  the  same,  but  representative  types.  The 
Ibex  of  the  Alps  differs,  for  instance,  from  that 
of  the  Pyrenees,  that  of  the  Pyrenees  from  those 
of  the  Caucasus  and  Himalayas,  these  again  from 
each  other  and  from  that  of  the  Altai. 

But  perhaps  the  most  conclusive  proof  that  we 
must  seek  for  the  origin  of  organic  life  outside 
of  physical  causes  consists  in  the  permanence  of 


40  THE  SILURIAN  BEACH. 

the  fundamental  types,  while  the  species  repre- 
senting these  types  have  differed  in  every  geologi- 
cal period.  Now  what  we  call  typical  features 
of  structure  are  in  themselves  no  more  stable  or 
permanent  than  specific  features.  If  physical 
causes,  such  as  light,  heat,  moisture,  food,  habits 
of  life,  etc.,  acting  upon  individuals,  have  gradu- 
ally in  successive  generations  changed  the  char- 
acter of  the  species  to  which  they  belong,  why 
not  that  of  the  class  and  the  branch  also  ?  If  we 
judge  this  question  from  the  material  side  at  all, 
we  must,  in  order  to  judge  it  fairly,  look  at  it 
wholly  from  that  point  of  view.  If  these  specific 
changes  are  brought  about  in  this  way,  it  is  be- 
cause external  causes  have  positive  permanent 
effects  upon  the  substances  of  which  animals  are 
built :  they  have  power  to  change  their  hair,  to 
change  their  skin,  to  change  certain  external 
appendages  or  ornamentations,  and  any  other  of 
those  ultimate  features  which  naturalists  call 
specific  characters.  Now  I  would  ask  what 
there  is  in  the  substances  out  of  which  class 
characters  are  built  that  would  make  them  less 
susceptible  to  such  external  influences  than  these 
specific  characters.  In  many  instances  the  for- 
mer are  more  delicate,  more  sensitive,  far  more 
fragile  and  transient  in  their  material  nature 
than  the  latter.  And  yet  never,  in  all  the 
chances  and  changes  of  time,  have  we  seen  any 


THE  SILUEIAN  BEACH.  41 

alteration  in  the  mode  of  respiration,  of  repro- 
duction, of  circulation,  or  in  any  of  the  systems 
of  organs  which  characterize  the  more  compre- 
hensive groups  of  the  Animal  Kingdom,  although 
they  are  quite  as  much  under  the  immediate  in- 
fluence of  physical  causes  as  those  structural  fea- 
tures which  have  been  constantly  changing. 

The  woody  fibre  of  the  Pine-trees  has  had  the 
same  structure  from  the  Carboniferous  age  to 
this  day,  while  their  mode  of  branching  and  the 
forms  of  their  cones  and  leaves  have  been  differ- 
ent in  each  period  according  to  their  respective 
species.  The  combination  of  rings,  the  structure 
of  the  wings,  and  the  articulations  of  the  legs 
are  the  same  in  the  Cockroaches  of  the  Carbon- 
iferous age  as  in  those  which  infest  our  ships  and 
our  dwellings  to-day,  while  the  proportion  of 
their  parts  is  on  quite  another  scale.  The  tissue 
of  the  Corals  in  the  Silurian  age  is  identical  in 
chemical  combination  and  organic  structure  with 
that  of  the  Corals  of  our  modern  reefs,  and  yet 
the  extensive  researches  upon  this  class,  for  which 
we  are  indebted  to  Milne  Edwards  and  Haime, 
have  not  revealed  a  single  species  extending 
through  successive  geological  ages,  but  show  us, 
on  the  contrary,  that  every  age  has  had  its  own 
kinds,  differing  among  themselves  in  the  same 
way  as  those  of  the  Gulf  of  Mexico  differ  now 
from  those  of  the  Indian  Ocean  and  the  Pacific. 


42  THE  SILURIAN  BEACH. 

The  scales  of  the  oldest  known  fishes  in  the  Silu- 
rian beds  have  the  same  microscopic  structure  as 
those  of  their  representative  types  to-day,  and  yet 
I  have  never  seen  a  single  fossil  fish  presenting 
the  same  specific  characters  in  the  successive  geo- 
logical epochs.  The  teeth  of  the  oldest  Sharks 
show  the  same  microscopic  structure  as  those  of 
the  present  time,  and  we  do  not  lack  opportuni- 
ties for  comparison,  since  the  former  are  as  com- 
mon in  the  mountain-limestone  of  Ireland  as  are 
those  of  the  living  Sharks  on  any  beach  where 
our  fishermen  boil  them  for  the  sake  of  their  oil, 
and  yet  the  Sharks  appear  under  different  generic 
and  specific  forms  in  each  geological  age. 

But  without  multiplying  examples,  which 
might  be  adduced,  ad  infinitum,  to  show  perma- 
nence of  type  combined  with  repeated  changes 
of  species,  suffice  it  to  say,  that,  while  the  gen- 
eral features  in  the  framework  of  the  organic 
world  and  the  materials  of  which  that  framework 
is  built,  though  quite  as  subject  to  the  influence 
of  physical  external  circumstances  as  any  so- 
called  specific  features,  have  remained  perfectly 
intact  from  the  beginning  of  Creation  till  now, 
so  that  not  the  smallest  difference  is  to  be  dis- 
cerned in  these  respects  between  the  oldest  repre- 
sentatives of  the  oldest  types  in  the  oldest  Silu 
rian  rocks  and  their  successors  through  all  the 
geological  ages  up  to  the  present  day,  the  species 


THE   SILURIAN  BEACH.  43 

have  been  different  in  each  epoch.  And  those 
still  deeper  ideal  relations,  the  plans  or  structu- 
ral conceptions  upon  which  animals  are  based, 
are  adhered  to  through  all  time  with  a  tenacity 
in  strange  contrast  to  the  perishableness  of  the 
material  forms  through  which  they  are  ex- 
pressed. 

It  is  surely  a  fair  question  to  ask  the  advocates 
of  the  transmutation  theory,  whether  they  attrib- 
ute to  physical  laws  the  discernment  that  would 
lead  them  to  change  the  specific  features,  but  to 
respect  all  those  characters  by  which  the  higher 
structural  combinations  of  the  Animal  Kingdom 
are  preserved  without  alteration,  —  in  other 
words,  to  maintain  the  organic  plan,  while  con- 
stantly diversifying  the  mode  of  expressing  it. 
If  so,  it  would  perhaps  be  as  well  to  call  such 
laws  by  another  name,  since  they  show  all  the 
comprehensive  wisdom  of  an  intelligent  Creator. 
Until  they  can  tell  us  why  certain  features  of 
animals  and  plants  are  permanent  under  condi- 
tions which,  according  to  their  view,  have  power 
to  change  certain  other  features  no  more  perish- 
able or  transient  in  themselves,  the  supporters  of 
the  development  theory  will  have  failed  to  sub- 
stantiate their  peculiar  scientific  doctrine. 

But  this  discussion  has  led  us  far  away  from 
our  starting-point,  and  interrupted  our  walk 


44  THE  SILURIAN  BEACH. 

along  the  Silurian  beach ;  let  us  return  to  gather 
a  few  specimens  there,  and  compare  them  with 
the  more  familiar  ones  of  our  own  shores.  I 
have  said  that  the  beach  was  a  shelving  one,  and 
covered  of  course  with  shoal  waters ;  but  as  I 
have  no  desire  to  mislead  my  readers,  or  to  pre- 
sent truths  as  generally  accepted  which  are  still 
subject  to  dispute,  I  would  state  here  that  the 
parallel  ridges  trending  east  to  west  across  the 
State  of  New  York,  considered  by  some  geolo- 
gists as  the  successive  shores  of  a  receding  ocean, 
are  believed  by  others  to  be  the  inequalities  on 
the  bottom  of  a  shallow  sea.  Not  only,  however, 
does  the  general  character  of  these  successive 
terraces  suggest  the  idea  that  they  must  have 
been  shores,  but  the  ripple-marks  upon  them  are 
as  distinct  as  upon  any  modern  beach.  The  reg- 
ular rise  and  fall  of  the  water  is  registered  there 
in  waving,  undulating  lines  as  clearly  as  on  the 
sand-beaches  of  Newport  or  Nahant ;  and  we  can 
see  on  any  one  of  those  ancient  shores  the  track 
left  by  the  waves  as  they  rippled  back  at  ebb  of 
the  tide  thousands  of  centuries  ago.  One  can 
often  see  where  some  obstacle  interrupted  the 
course  of  the  water,  causing  it  to  break  around 
it ;  and  such  an  indentation  even  retains  the  soft, 
muddy,  plastic  look  that  we  observe  on  the  pres- 
ent beaches,  where  the  resistance  made  by  any 
pebble  or  shell  to  the  retreating  wave  has  given 


THE  SILUKIAN  BEACH.  45 

it  greater  force  at  that  point,  so  that  the  sand 
around  the  spot  is  soaked  and  loosened.  There 
is  still  another  sign,  equally  familiar  to  those  who 
have  watched  the  action  of  water  on  a  beach. 
Where  a  shore  is  very  shelving  and  flat,  so  that 
the  waves  do  not  recede  in  ripples  from  it,  but  in 
one  unbroken  sheet,  the  sand  and  small  pebbles 
are  dragged  and  form  lines  which  diverge  when- 
ever the  water  meets  an  obstacle,  thus  forming 
sharp  angles  on  the  sand.  Such  marks  are  as 
distinct  on  the  oldest  Silurian  rocks  as  if  they 
had  been  made  yesterday.  Nor  are  these  the 
only  indications  of  the  same  fact.  There  are  cer 
tain  animals  living  always  upon  sandy  or  muddy 
shores,  which  require  for  their  well-being  that 
the  beach  should  be  left  dry  a  part  of  the  day. 
These  animals,  moving  about  in  the  sand  or  mud 
from  which  the  water  has  retreated,  leave  their 
tracks  there  ;  and  if,  at  such  a  time,  the  wind  is 
blowing  dust  over  the  beach,  and  the  sun  is  hot 
enough  to  bake  it  upon  the  impressions  so  formed, 
they  are  left  in  a  kind  of  mould.  Such  trails  and 
furrows,  made  by  small  Shells  or  Crastacea,  are 
also  found  in  plenty  on  the  oldest  deposits. 

Admitting  it,  then,  to  be  a  beach,  let  us  begin 
with  the  lowest  type  of  the  Animal  Kingdom, 
and  see  what  Radiates  are  to  be  found  there. 
There  are  plenty  of  Corals,  but  they  are  not  the 
same  kinds  of  Corals  as  those  that  build  up  our 


46  THE   SILURIAN  BEACH. 

reefs  and  islands  now.     The  modern  Coral  ani- 
mals are  chiefly  Polyps,  but  the  prevailing  Corals 
of  the  Silurian  age  were  Acalephian  Hydroids, 
animals  which  indeed  resemble  Polyps  in  certain 
external  features,  and  have  been  mistaken  for 
them,  but  which  are  nevertheless  Acalephs  by 
their  internal   structure.     In  these   Corals   the 
body,  instead  of  being  divided  into  chambers  by 
the  vertical  partitions   so   characteristic  of  the 
Polyps,  is  divided  at  regular  distances  by  hori- 
zontal   floors.      I    subjoin    a 
wood-cut  of  a  Silurian  Coral, 
which  does  not,  however,  show 
the  peculiar  internal  structure, 
but  gives  some  idea  of  the  gen- 
eral appearance  of  the  old  Hy- 
droid   Corals.      We  have  but 
one  Acalephian  Coral  now  living,  the  Millepore ; 
and  it  was  by  comparing  that  with  these  ancient 
ones  that  I  first  detected  their  relation  to  the  Aca- 
lephs.    For  the  true  Acalephs  or  Jelly-Fishes  we 
shall  look  in  vain ;  but  the  presence  of  the  Aca- 
lephian Corals   establishes  the  existence  of  the 
type,  and  we  cannot  expect  to  find  those  kinds 
preserved  which   are   wholly  destitute   of  hard 
parts.     I  do  not  attempt  any  description  of  the 
Polyps  proper,  because  the  early  Corals  of  that 
class  are  comparatively  few,  and  do  not  present 
features  sufficiently  characteristic  to  attract  the 
notice  of  the  casual  observer. 


THE   SILUKIAN  BEACH.  47 

Of  the  Echinoderms,  the  class  of  Radiates  rep- 
resented now  by  our  Star-Fishes  and  Sea-Urchins, 
we  may  gather  any  quantity,  though  the  old-fash- 
ioned forms  are  very  different  from  the  living  ones. 
I  have  dwelt  at  such  length  in  a  former  article  * 
on  the  wonderful  beauty  and  variety  of  the  Cri- 
noids,  or  "  Stone  Lilies,"  as  they  have  been  called, 
from  their  resemblance  to  flowers,  that  I  will  only 
briefly  allude  to  them  here.  The  subjoined  wood- 
cut represents  one  with  a  closed  cup  ;  but  the 
number  of  their  different  pat- 
terns is  hardly  to  be  counted, 
and  I  would  invite  any  one  who 
questions  the  abundant  expres- 
sion of  life  in  those  days  to  look 
at  some  slabs  of  ancient  lime- 
stone in  the  Zoological  Museum 
at  Cambridge,  where  the  stems 
of  the  Crinoids  are  tangled  to- 
gether as  thickly  as  sea-weed 
on  the  shore.  Indeed,  some 
of  our  rock-deposits  consist 
chiefly  of  the  fragments  of  their 
remains. 

The  Mollusks  were  also  rep- 
resented then,  as  now,  by  their  three  classes,  — 
Acephala,  Gasteropoda,  and  Cephalopoda.     The 

*   See   Methods   of    Study   in    Natural    History,    Atlantic 
Monthly,  No.  LVIL,  July,  1862. 


48  THE  SILURIAN  BEACH. 

Acepliala  or  Bivalves  we  shall  find  in  great  num- 
bers, but  of  a  very  different  pattern  from  the 
Oysters,  Clams,  and  Mussels  of  recent  times. 
The  annexed  wood-cut  represents  one  of  these 
Brachiopods,  which  form 
a  very  characteristic  type 
of  the  Silurian  deposits. 
The  square  cut  of  the 
upper  edge,  where  the 
two  valves  meet  along  the  back  and  are  united  by 
a  hinge,  is  altogether  old-fashioned,  and  unknown 
among  our  modern  Bivalves.  The  wood-cut  does 
not  show  the  inequality  of  the  two  valves,  also  a 
very  characteristic  feature  of  this  group,  —  one 
valve  being  flat  and  fitting  closely  into  the  other, 
which  is  more  spreading  and  much  fuller.  These, 
also,  were  represented  by  a  great  variety  of  spe- 
cies, and  we  find  them  crowded  together  as  closely 
in  the  ancient  rocks  as  Oysters  or  Clams  or  Mus- 
sels on  any  of  our  modern  shores.  Besides  these, 
there  were  the  Bryozoa,  a  small  kind  of  com- 
pound Mollusk  allied  to  the  Clams,  and  very  busy 
then  in  the  ancient  Coral  work.  They  grew  in 
communities,  and  the  separate  individuals  are  so 
minute  that  a  Bryozoan  stock  looks  like  some 
delicate  moss.  They  still  have  their  place  among 
the  Reef-Building  Corals,  but  play  an  insignifi- 
cant part  in  comparison  with  that  of  their  prede- 
cessors. 


\ 

THE  SILURIAN  BEACH.  49 

Of  the  Silurian  Univalves  or  Gasteropods  there 
is  not  much  to  tell,  for  their  spiral  shells  were  so 
brittle  that  scarcely  any  perfect  specimens  are 
known,  though  their  broken  remains  are  found 
in  such  quantities  as  to  show  that  this  class  also 
was  very  fully  represented  in  the  earliest  crea- 
tion. But  the  highest  class  of  Mollusks,  the 
Cephalopods  or  Chambered  Shells,  or  Cuttle- 
Fishes,  as  they  are  called  when  the  animal  is  un- 
protected by  a  shell,  are,  on  the  contrary,  very 
well  preserved,  and  they  are  very  numerous.  Of 
these  I  will  speak  somewhat  more  in  detail,  be- 
cause their  geological  history  is  a  very  curious 
one. 

The  Chambered  Nautilus  is  familiar  to  all, 
since,  from  the  exquisite  beauty  of  its  shell,  it  is 
especially  sought  for  by  conchologists ;  but  it  is 
nevertheless  not  so  common  in  our  days  as  the 
Squids  and  Cuttle-Fishes,  which  are  the  most 
numerous  modern  representatives  of  the  class. 
In  the  earliest  geological  days,  on  the  contrary, 
those  with  a  shell  predominated,  differing  from 
the  later  ones,  however,  in  having  the  shell  per- 
fectly straight  instead  of  curved,  though  its  in- 
ternal structure  was  the  same  as  it  is  now  and 
has  ever  been.  Then,  as  now,  the  animal  shut 
himself  out  from  his  last  year's  home,  building 
his  annual  wall  behind  him,  till  his  whole  shell 
was  divided  into  successive  chambers,  all  of 

3  D 


50  THE  SILURIAN  BEACH. 

which  were  connected  by  a  siphon.  Some  of  the 
shells  of  this  kind  belonging  to  the  Silurian  de- 
posits are  enormous :  giants  of  the  sea  they  must 
have  been  in  those  days.  They  have  been  found 
fifteen  feet  long,  and  as  large  round  as  a  man's 
body.  One  can  imagine  that  the  Cuttle-Fish  in- 
habiting such  a  shell  must  have  been  a  formi- 
dable animal.  These  straight  chambered  shells 
of  the  Silurian  and  Devonian  seas  are 
called  Orthoceratites  (see  accompany- 
ing wood-cut).  We  shall  meet  them 
again  hereafter,  under  another  name 
and  with  a  different  form ;  for,  as  they 
advance  in  the  geological  ages,  they 
not  only  assume  the  curved  outline  with 
ever  closer  whorls  till  it  culminates  in 
the  compact  coil  of  the  Ammonites  of 
the  middle  periods,  but  the  partitions, 
which  are  perfectly  plain  walls  in  these 
earlier  forms,  become  scalloped  and  in- 
voluted along  the  edges  in  the  later 
ones,  making  the  most  delicate  and 
exquisite  tracery  on  the  surface  of  the 
shell. 

Of  Articulates  we  find  only  two  classes,  Worms 
and  Crustacea.  Insects  there  were  none,  —  for, 
as  we  have  seen,  this  early  world  was  wholly 
marine.  There  is  little  to  be  said  of  -the 
Worms,  for  their  soft  bodies,  unprotected  by 


THE   SILURIAN  BEACH.  51 

any  hard  covering,  could  hardly  be  preserved ; 
but,  like  the  marine  Worms  of  our  own  times, 
they  were  in  the  habit  of  constructing  envel- 
opes for  themselves,  built  of  sand,  or  some- 
times from  a  secretion  of  their  own  bodies,  and 
these  cases  we  find  in  the  earliest  deposits,  giving 
us  assurance  that  the  Worms  were  represented 
there.  I  should  add,  however,  that  many  im- 
pressions described  as  produced  by  Worms  are 
more  likely  to  have  been  the  tracks  of  Crustacea. 
But  by  far  the  most  characteristic  class  of  Ar- 
ticulates in  ancient  times  were  the  Crustaceans. 
The  Trilobites  stand  in  the  same  relation  to  the 
modern  Crustacea  as  the  Crinoids  do  to  the  mod- 
ern Echinoderms.  They  were  then  the  sole  rep- 
resentatives of  the  class,  and  the  variety  and  rich- 
ness of  the  type  are  most  extraordinary.  They 
were  of  nearly  equal  breadth  for  the  whole 
length  of  the  body,  and  rounded  at  the  two 
ends,  so  as  to  form  an  oval  outline.  To  give  any 
adequate  idea  of  the  number  and  variety  of  spe- 
cies would  fill  a  volume,  but  I  may  enumerate 
some  of  the  more  striking  differences :  as,  for  in- 
stance, the  greater  or  less  prominence  of  the  an- 
terior shield,  —  the  preponderance  of  the  poste- 
rior end  in  some,  while  in  others  the  two  ends 
are  nearly  equal,  —  the  presence  or  absence  of 
prongs  on  the  shield  and  of  spines  along  the 
sides  of  the  body,  —  appendages  on  the  head  in 


52  THE  SILUEIAN  BEACH. 

some  species,  of  which  others  are  entirely  desti- 
tute, —  and  the  smooth  outline  of  some,  while  in 
others  the  surface  is  broken  by  a  variety  of  ex- 
ternal ornamentation.  Such  are  a  few  of  the 
more  prominent  differences  among  them.  But 
the  general  structural  features  are  the  same  in 
all.  The  middle  region  of  the  body  is  always 
divided  in  uniform  rings,  lobed  in  the  middle  so 
as  to  make  a  ridge  along  the  back  with  a  slight 
depression  on  either  side  of  it.  It  is  from  this 
three-lobed  division  that  they  receive  their  name. 
The  subjoined  wood-cut  represents  a  character- 
istic Silurian  Trilobite. 

There  is  no  group  more 
prominent  in  the  earliest  cre- 
ations than  this  one  of  the 
Trilobites,  and  so  exclusively 
do  they  belong  to  them,  that, 
as  we  shall  see,  in  proportion 
as  the  later  representatives 
of  the  class  come  in,  these 
old-world  Crustaceans  drop 
out  of  the  ranks,  fall  behind, 
as  it  were,  in  the  long  pro- 
cession of  animals,  and  are  left  in  the  ancient 
deposits.  Even  in  the  Carboniferous  period  but 
few  are  to  be  found :  they  had  their  day  in  the 
Silurian  and  Devonian  ages.  In  consequence  of 
their  solid  exterior,  the  preservation  of  these  ani- 


THE  SILURIAN  BEACH.  53 

mals  is  very  complete ;  and  their  attitudes  are 
often  so  natural,  and  the  condition  of  all  their 
parts  so  perfect,  that  one  would  say  they  had 
died  yesterday  rather  than  countless  centuries 
ago. 

Their  geological  history  has  been  very  thor- 
oughly studied;  not  only  are  we  familiar  with 
all  their  adult  characters,  but  even  their  embry- 
ology is  well  known  to  naturalists.  It  is,  indeed, 
wonderful  that  the  mode  of  growth  of  animals 
which  died  out  in  the  Carboniferous  period  should 
be  better  known  to  us  than  that  of  many  living 
types.  But  it  is  nevertheless  true  that  their  em- 
bryonic forms  have  been  found  perfectly  pre- 
served in  the  rocks,  and  Barrande,  in  his  "  Sys- 
tSme  Silurien  de  la  Boh£me,"  gives  us  all  the 
stages  of  their  development,  from  the  time  when 
the  animal  is  merely  sketched  out  as  a  simple 
furrow  in  the  embryo  to  its  mature  condition. 
So  complete  is  the  sequence,  that  the  plate  on 
which  their  embryonic  changes  are  illustrated 
contains  more  than  thirty  figures,  all  represent- 
ing different  phases  of  their  growth.  There  is 
not  a  living  Crab  represented  so  fully  in  any  of 
our  scientific  works  as  is  that  one  species  of  Tri- 
lobite  whose  whole  story  Barrande  has  traced 
from  the  egg  to  its  adult  size.  Such  facts  should 
make  those  who  rest  their  fanciful  theories  of  the 
origin  and  development  of  life  on  the  imperfec- 


54  THE   SILURIAN  BEACH. 

tion  of  the  geological  record,  filling  up  the  sup- 
posed lapses  to  suit  themselves,  more  cautious  as 
to  their  results. 

We  have  found,  then,  Radiates,  Mollusks,  and 
Articulates  in  plenty ;  and  now  what  is  to  be  said 
of  Vertebrates  in  these  old  times,  —  of  the  high- 
est and  most  important  division  of  the  Animal 
Kingdom,  that  to  which  we  ourselves  belong? 
They  were  represented  by  Fishes  alone ;  and  the 
Fish  chapter  in  the  history  of  the  early  organic 
world  is  a  curious,  and,  as  it  seems  to  me,  a  very 
significant  one.  We  shall  find  no  perfect  speci- 
mens ;  and  he  would  be  a  daring,  not  to  say  a 
presumptuous  thinker,  who  would  venture  to  re- 
construct a  fish  of  the  Silurian  age  from  any 
remains  that  are  left  to  us.  But  still  we  find 
enough  to  indicate  clearly  the  style  of  those  old 
fishes,  and  to  show,  by  comparison  with  the  living 
types,  to  what  group  of  modern  times  they  be- 
long. We  should  naturally  expect  to  find  the 
Vertebrates  introduced  in  their  simplest  form ; 
but  this  is  by  no  means  the  case :  the  common 
fishes,  as  Cod,  Herring,  Mackerel,  and  the  like, 
were  unknown  in  those  days. 

But  there  are  two  groups  of  so-called  fishes, 
differing  from  these  by  some  marked  features, 
among  which  we  may  find  the  modern  represent- 
atives of  these  earliest  Vertebrates.  Of  these 
two  groups  one  consists  chiefly  now  of  the  Gar- 


THE  SILURIAN  BEACH.  55 

Pikes  of  our  Western  waters,  though  the  Stur- 
geons share  also  in  some  of  their  features.  In 
these  fishes  there  is  a  singular  union  of  reptilian 
with  fish-like  characters.  The  systems  of  circu- 
lation and  of  respiration  in  them  are  more  com- 
plicated than  in  the  common  fishes;  the  struc- 
ture of  the  skull  resembles  that  of  the  skull  in 
reptiles,  and  they  have  other  reptilian  characters, 
such  as  their  ability  to  move  the  head  upon  the 
neck  independently  of  the  body,  and  the  connec- 
tion of  the  vertebrae  by  ball-and-socket  joint,  in- 
stead of  by  inverted  cones,  as  in  the  ordinary 
fishes.  Their  scales  are  also  peculiar,  being  cov- 
ered by  enamel  so  hard,  that,  if  struck  with  steel, 
they  will  emit  sparks  like  flint.  It  is  on  account 
of  this  peculiarity  that  the  whole  group  has  been 
called  Ganoid.  Now,  though  we  have  not  found 
as  yet  any  complete  specimens  of  Silurian  fishes, 
their  disconnected  remains  are  scattered  profusely 
in  the  early  deposits.  The  scales,  parts  of  the 
backbone,  parts  of  the  skull,  the  teeth,  are  found 
in  a  tolerable  state  of  preservation ;  and  these  in- 
dications, fragmentary  as  they  are,  give  us  the 
clew  to  the  character  of  the  most  ancient  fishes. 
A  large  proportion  of  them  were  no  doubt  Gan- 
oids ;  for  they  had  the  same  peculiar  articulation 
of  the  vertebras,  the  flexibility  of  the  neck,  and 
the  hard  scales  so  characteristic  of  our  Gar- 
Pikes. 


56  THE  SILURIAN  BEACH. 

There  is  another  type  of  these  ancient  Verte- 
brates which  has  also  its  representatives  among 
our  modern  fishes.  These  are  the  Sharks  and 
Skates,  or,  as  the  Greeks  used  to  call  them,  the 
Selachians,  —  making  a  very  appropriate  distinc- 
tion between  them  and  common  fishes,  on  ac- 
count of  the  difference  in  the  structure  of  the 
skeleton.  In  Selachians  the  quality  of  the  bones 
is  granular,  instead  of  fibrous,  as  in  fishes ;  the 
arches  above  and  below  the  backbone  are  formed 
by  flat  plates,  instead  of  the  spines  so  character- 
istic of  all  the  fish  proper ;  and  the  skull  consists 
of  a  solid  box,  instead  of  being  built  of  overlap- 
ping pieces  like  the  true  fish-skull.  They  differ 
also  in  their  teeth,  which,  instead  of  being  im- 
planted in  the  bone  by  a  root,  as  in  fishes,  are 
loosely  set  in  the  gum  without  any  connection 
with  the  bone,  and  are  movable,  being  arranged 
in  several  rows  one  behind  another,  the  back  rows 
moving  forward  to  take  the  place  of  the  front 
ones  when  the  latter  are  worn  off.  They  are  un- 
like the  common  fishes  also  in  having  the  back- 
bone continued  to  the  very  end  of  the  tail,  which 
is  cut  in  uneven  lobes,  the  upper  lobe  being  the 
longer  of  the  two,  while  the  terminal  fin,  so  con- 
stant a  feature  in  fishes,  is  wanting.  The  Se- 
lachians resemble  higher  Vertebrate  types  not 
only  in  the  small  number  of  their  eggs,  and  in 
the  closer  connection  of  the  young  with  the 


THE  SILUBIAN  BEACH.  57 

mother,  but  also  in  their  embryological  develop- 
ment, which  has  many  features  in  common  with 
that  of  birds  and  turtles.  Of  this  group,  also, 
we  find  numerous  remains  in  the  ancient  geologi- 
cal deposits ;  and  though  we  have  not  the  means 
of  distinguishing  the  species,  we  have  ample  evi- 
dence for  determining  the  type. 

This  combination  of  higher  with  lower  fea- 
tures in  the  earlier  organic  forms  is  very  striking, 
and  becomes  still  more  significant  when  we  find: 
that  many  of  the  later  types  recall  the  more  an- 
cient ones.  I  have  called  these  more  compre- 
hensive groups  of  former  times,  combining  char- 
acters of  different  classes,  synthetic  or  prophetic 
types ;  and  we  might  as  fitly  give  the  name  of 
retrospective  types  to  many  of  the  later  groups, 
for  they  recall  the  past,  as  the  former  anticipate 
the  future.  And  it  is  not  only  among  the  Fishes 
and  the  Reptiles  that  we  find  these  combinations. 
The  most  numerous  of  the  ancient  Radiates  are 
the  Acalephian  Corals,  combining,  in  the  Hydroid 
form,  the  Polyp-like  mode  of  life,  habits,  and  gen- 
eral appearance  with  the  structure  of  Acalephs. 
The  Crinoids,  with  the  closed  cups  in  some,  and 
the  open,  star-like  crowns  in  others,  unite  fea- 
tures of  the  present  Star-Fishes  and  Sea-Urchins, 
and,  by  their  stem  attaching  them  to  the  ground, 
include  also  a  Polyp-like  character;  while  the 
Trilobites,  with  their  uniform  rings  and  their 

3* 


58  THE  SILURIAN  BEACH." 

prominent  anterior  shield,  unite  characters  of 
Worms  and  Crustacea. 

These  early  types  seem  to  sketch  in  broad,  gen- 
eral characters  the  Creative  purpose,  and  to  in- 
clude in  the  first  average  expression  of  the  plan 
all  its  structural  possibilities.  The  Crinoid  forms 
include  the  thought  of  the  modern  Star-Fishes 
and  Sea-Urchins ;  the  simple  chambered  shells 
of  the  Silurian  anticipate  the  more  complicated 
structure  of  the  later  ones ;  the  Trilobites  give 
the  most  comprehensive  expression  of  the  Articu- 
late type ;  while  the  early  Fishes  not  only  proph- 
esy the  Reptiles  which  are  to  come,  but  also  hint 
at  Birds  and  even  at  Mammalia  by  their  embry- 
onic development  and  their  mode  of  reproduc- 
tion. 

Looked  at  from  this  point  of  view,  the  animal 
world  is  an  intellectual  Creation,  complete  in  all 
its  parts,  and  coherent  throughout ;  and  when  we 
find.,  that,  although  these  ancient  types  have  be- 
come obsolete  and  been  replaced  by  modern  ones, 
yet  there  are  always  a  few  old-fashioned  individ- 
uals, left  behind,  as  it  were,  to  give  the  key  to 
the  history  of  their  race,  as  the  Gar-Pike,  for  in- 
stance, to  explain  the  ancient  Fishes,  the  Mille- 
pore  to  explain  the  old  Acalephian  Corals,  the 
Nautilus  to  be  the  modern  exponent  of  the  Am- 
monites and  Orthoceratites  of  past  times,  we  can- 
not avoid  the  impression  that  this  Creative  work 


-THE  SILURIAN  BEACH.  59 

has  been  intended  also  to  be  educational  for  Man, 
and  to  teach  him  his  own  relation  to  the  organic 
world.  The  embryology  of  the  modern  types 
confirms  this  idea,  for  here  we  find  an  epitome 
of  their  geological  history.  The  embryo  of  the 
present  Star-Fishes  recalls  the  Crinoids  ;  the  em- 
bryo of  the  Crab  recalls  the  Trilobites ;  the  em- 
bryo of  the  Vertebrates ,  including  even  that  of 
the  higher  Mammalia,  recalls  the  ancient  Fishes. 
Does  not  this  fact,  that  the  individual  animal  in 
its  growth  recalls  the  history  of  its  type,  prove 
that  the  Creative  Thought  in  its  immediate  pres- 
ent action  embraces  all  that  has  gone  before,  as 
its  first  organic  expression  included  all  that  was 
to  come  ?  The  study  of  Nature  in  its  highest 
meaning  shows  us  the  present  doubly  rich  with 
all  the  past,  and  the  past  linked  and  interwoven 
with  the  present,  not  lying  divorced  and  dead 
behind  it. 

I  have  spoken  of  the  Silurian  beach  as  if  there 
were  but  one,  not  only  because  I  wished  to  limit 
my  sketch,  and  to  attempt  at  least  to  give  it  the 
vividness  of  a  special  locality,  but  also  because  a 
single  such  shore  will  give  us  as  good  an  idea  of 
the  characteristic  fauna  of  the  time  as  if  we  drew 
our  material  from  a  wider  range.  There  are, 
however,  a  great  number  of  parallel  ridges  be- 
longing to  the  Silurian  and  Devonian  periods, 
running  from  east  to  west,  not  only  through  the 


60  THE  SILURIAN  BEACH. 

State  of  New  York,  but  far  beyond,  through  the 
States  of  Michigan  and  Wisconsin  into  Minne- 
sota ;  one  may  follow  nine  or  ten  such  successive 
shores  in  unbroken  lines,  from  the  neighborhood 
of  Lake  Champlain  to  the  Far  West.  They  have 
all  the  irregularities  of  modern  sea-shores,  run- 
ning up  to  form  little  bays  here,  and  jutting  out 
in  promontories  there ;  and  upon  each  one  are 
found  animals  of  the  same  kind,  but  differing  in 
species  from  those  of  the  preceding. 

Although  the  early  geological  periods  are  more 
legible  in  North  America,  because  they  are  ex- 
posed over  such  extensive  tracts  of  land,  yet  they 
have  been  studied  in  many  other  parts  of  the 
globe.  In  Norway,  in  Germany,  in  France,  in 
Russia,  in  Siberia,  in  Kamtschatka,  in  parts  of 
South  America,  in  short,  wherever  the  civiliza- 
tion of  the  white  race  has  extended,  Silurian  de- 
posits have  been  observed,  and  everywhere  they 
bear  the  same  testimony  to  a  profuse  and  varied 
creation.  The  earth  was  teeming  then  with  life 
as  now,  and  in  whatever  corner  of  its  surface  the 
geologist  finds  the  old  strata,  they  hold  a  dead 
fauna  as  numerous  as  that  which  lives  and  moves 
above  it.  Nor  do  we  find  that  there  was  any 
gradual  increase  or  decrease  of  any  organic  forms 
at  the  beginning  and  close  of  the  successive  peri- 
ods. On  the  contrary,  the  opening  scenes  of 
every  chapter  in  the  world's  history  have  been 


THE   SILUKIAN  BEACH.  61 

crowded  with  life,  and  its  last  leaves  as  full  and 
varied  as  its  first. 

I  think  the  impression  that  the  faunae  of  the 
early  geological  periods  were  more  scanty  than 
those  of  later  times  arises  partly  from  the  fact 
that  the  present  creation  is  made  a  standard 
of  comparison  for  all  preceding  creations.  Of 
course,  the  collections  6f  living  types  in  any 
museum  must  be  more  numerous  than  those  of 
fossil  forms,  for  the  simple  reason  that  almost 
the  whole  of  the  present  surface  of  the  earth, 
with  the  animals  and  plants  inhabiting  it,  is 
known  to  us,  whereas  the  deposits  of  the  Silurian 
and  Devonian  periods  are  exposed  to  view  only 
over  comparatively  limited  tracts  and  in  discon- 
nected regions.  But  let  us  compare  a  given  ex- 
tent of  Silurian  or  Devonian  sea-shore  with  an 
equal  extent  of  sea-shore  belonging  to  our  own 
time,  and  we  shall  soon  be  convinced  that  the 
one  is  as  populous  as  the  other.  On  the  New- 
England  coast  there  are  about  one  hundred  and 
fifty  different  kinds  of  fishes,  in  the  Gulf  of  Mex- 
ico two  hundred  and  fifty,  in  the  Red  Sea  about 
the  same.  We  may  allow  in  present  times  an 
average  of  two  hundred  or  two  hundred  and  fifty 
different  kinds  of  fishes  to  an  extent  of  ocean 
covering  about  four  hundred  miles.  Now  I  have 
made  a  special  study  of  the  Devonian  rocks  of 
Northern  Europe,  in  the  Baltic  and  along  the 


62  THE  SILURIAN  BEACH. 

shore  of  the  German  Ocean.  I  have  found  in 
those  deposits  alone  one  hundred  and  ten  kinds 
of  fossil  fishes.  To  judge  of  the  total  number 
of  species  belonging  to  those  early  ages  by  the 
number  known  to  exist  now  is  about  as  reason- 
able as  to  infer  that  because  Aristotle,  familiar 
only  with  the  waters  of  Greece,  recorded  less 
than  three  hundred  kinds  of  fishes  in  his  limited 
fishing-ground,  therefore  these  were  all  the  fishes 
then  living.  The  fishing-ground  of  the  geologist 
in  the  Silurian  and  Devonian  periods  is  even 
more  circumscribed  than  his,  and  belongs,  be- 
sides, not  to  a  living,  but  to  a  dead  world,  far 
more  difficult  to  decipher. 

But  th6  sciences  of  Geology  and  Palaeontology 
are  making  such  rapid  progress,  now  that  they 
go  hand  in  hand,  that  our  familiarity  with  past 
creations  is  daily  increasing.  We  know  already 
that  extinct  animals  exist  all  over  the  world: 
heaped  together  under  the  snows  of  Siberia, — 
lying  thick  beneath  the  Indian  soil,  —  found 
wherever  English  settlers  till  the  ground  or  work 
the  mines  of  Australia,  —  figured  in  the  old  En- 
cyclopaedias of  China,  where  the  Chinese  philoso- 
phers have  drawn  them  with  the  accuracy  of  their 
nation,  —  built  into  the  most  beautiful  temples 
of  classic  lands,  for  even  the  stones  of  the  Par- 
thenon are  full  of  the  fragments  of  these  old  fos- 
sils, and  if  any  chance  had  directed  the  attention 


THE   SILURIAN  BEACH.  63 

of  Aristotle  towards  them,  the  science  of  Palae- 
ontology would  not  have  waited  for  its  founder 
till  Cuvier  was  born,  —  in  short,  in  every  corner 
of  the  earth  where  the  investigations  of  civilized 
men  have  penetrated,  from  the  Arctic  to  Patago- 
nia and  the  Cape  of  Good  Hope,  these  relics  tell 
us  of  successive  populations  lying  far  behind  our 
own,  and  belonging  to  distinct  periods  of  the 
world's  history. 


III. 

THE  FERN  FORESTS  OF  THE   CARBON- 
IFEROUS PERIOD. 

DRAW  two  lines  on  your  map,  the  upper  one 
running  from  the  mouth  of  the  St.  Law- 
rence westward  nearly  to  St.  Paul  on  the  Missis- 
sippi, and  the  lower  one  from  the  neighborhood 
of  St.  John's  in  Newfoundland,  running  south- 
westerly about  to  the  point  where  the  Wisconsin 
joins  the  Mississippi,  but  jutting  down  to  form  an 
extensive  peninsula  comprising  part  of  the  States 
of  Indiana  and  Illinois,  and  you  include  between 
them  all  of  the  United  States  which  existed  at 
the  close  of  the  Devonian  period.  The  upper 
line  rests  against  the  granite  hills  dividing  the 
Silurian  and  Devonian  deposits  of  the  British 
Possessions  to  the  north  from  those  of  the  United 
States  to  the  south,  Canada  itself  consisting,  in 
great  part,  of  the  granite  ridge. 

How  far  the  early  deposits  extended  to  the 
north  of  the  Laurentian  Hills,  as  well  as  the  out- 
line of  that  portion  of  the  continent  in  those 
times,  remains  still  very  problematical ;  but  the 


THE  FERN  FORESTS. 


65 


investigations  thus  far  undertaken  in  those  re- 
gions would  lead  to  the  supposition  that  the  same 
granite  upheaval  which  raised  Canada  stretched 
northward  in  a  broad,  low  ridge  of  land,  widen- 
ing in  its  upper  part  and  extending  to  the  neigh- 
borhood of  Bathurst  Inlet  and  King  William's 
Island,  while  on  either  side  of  it,  to  the  east  and 
west,  the  Silurian  and  Devonian  deposits  ex- 
tended far  toward  the  present  outlines  of  the 
continent.  These  fundamental  relations  of  the 
continents  are  admirably  presented  by  Professor 
Guyot  in  his  charming  volume  entitled,  "  Earth 
and  Man." 

Indeed,  our  geological  surveys,  as  well  as  the 
information  otherwise  obtained  concerning,  the 
primitive  condition  of  North,  America  and  the 
gradual  accessions  it  has  received  in  more  recent 
periods,  point  to  a  very  early  circumscription  of 
the  area  which,  in  the  course  of  time,  was  to  be- 
come the  continent  we  now  inhabit,  with  its  mod- 
ern features.  Not  only  from  the  geology  of 
America,  but  from  that  of  Europe  also$  it  would 
seem  that  the  position  of  the  continents  was 
sketched  out  very  early  in  the  progressive  devel-- 
opment  of  the  physical  constitution  of  our  earth. 
It  is  true  that  in  the  present  state  of  our  knowl- 
edge such  wide  generalizations  must  be  taken 
with  caution,  and  held  in  abeyance  to  the  addi- 
tional facts  which  future  investigations  may  de- 


66  THE  FERN  FORESTS  OF 

velop.  But  thus  far  the  results  certainly  do  not 
sustain  the  theories  which  have  lately  found  favor 
among  geologists,  of  entire  changes  in  the  rela- 
tive distribution  of  land  and  sea  and  in  the  con- 
nection of  continents  with  one  another ;  on  the 
contrary,  it  would  appear,  that,  in  accordance 
with  the  laws  of  all  organic  progress,  arising  from 
a  fixed  starting-point  and  proceeding  through 
regular  changes  toward  a  well-defined  end,  the 
continents  have  grown  steadily  and  consistently 
from  the  beginning,  through  successive  accessions 
in  a  definite  direction,  to  their  present  form  and 
organic  correlations.  If,  indeed,  there  is  any 
meaning  in  the  remarkably  symmetrical  combi- 
nations of  the  double  twin  continents  in  the 
Eastern  Hemisphere,  so  closely  soldered  in  their 
northern  half,  as  contrasted  with  the  single  pair 
in  the  Western  Hemisphere,  isolated  in  their  po- 
sition, but  so  strikingly  similar  in  their  outlines, 
they  must  be  the  result  of  a  progressive  and  pre- 
determined growth  already  hinted  at  in  the  rela- 
tive position  and  gradual  increase  of  the  first 
lands  raised  above  the  level  of  the  ocean. 

However  this  may  be,  there  can  be  no  doubt 
that  we  now  know  with  tolerable  accuracy  the 
limits  of  the  land  raised  above  the  water  in  the 
.earlier  geological  periods  in  the  present  United 
States.  Let  us  see,  then,  what  we  enclose  be- 
tween our  two  lines.  We  have  Newfoundland 


THE   CARBONIFEROUS  PERIOD.  67 

and  Nova  Scotia,  the  greater  part  of  New  Eng- 
land, the  whole  of  New  York,  a  narrow  strip 
along  the  north  of  Ohio,  a  great  part  of  Indiana 
and  Illinois,  and  nearly  the  whole  of  Michigan 
and  Wisconsin. 

Within  this  region  lie  all  the  Great  Lakes. 
The  origin  of  these  large  troughs,  holding  such 
immense  sheets  of  fresh  water,  remains  still  the 
subject  of  discussion  and  investigation  among 
geologists.  It  has  been  supposed  that,  in  the 
primitive  configuration  of  the  globe,  when  the 
formation  of  those  depressions  at  the  poles  in 
which  the  Arctic  seas  are  accumulated  gave  rise 
to  a  corresponding  protrusion  at  the  equator,  the 
curve  thus  produced  throughout  the  North  Tem- 
perate Zone  may  have  forced  up  the  Canada 
granite,  and  have  caused,  at  the  same  time,  those 
rents  in  the  earth's  surface  now  filled  by  the 
Canada  lakes  ;  and  this  view  is  sustained  by  the 
fact  that  there  is  a  belt  of  lakes,  among  which, 
however,  the  Canada  lakes  are  far  the  largest,  all 
around  the  world  in  that  latitude.  The  geologi- 
cal phenomena  connected  with  all  these  lakes 
have  not,  however,  been  investigated  with  suffi- 
cient accuracy  and  detail,  nor  has  there  been  any 
comparison  of  them  extensive  and  comprehensive 
enough  to  justify  the  adoption  of  any  theory  re- 
specting their  origin.  In  an  excursion  to  Lake 
Superior,  some  years  since,  I  satisfied  myself  that 


68  THE  FEEN  FORESTS  OF 

the  position  and  outline  of  that  particular  lake 
had  their  immediate  cause  in  several  distinct  sys- 
tems of  dikes  which  intersect  its  northern  shore, 
and  have  probably  cut  up  the  whole  tract  of  rock 
over  the  space  now  filled  by  that  wonderful  sheet 
of  fresh  water  in  such  a  way  as  to  destroy  its 
continuity,  to  produce  depressions,  and  gradually 
create  the  excavation  which  now  forms  the  basin 
of  the  lake.  How  far  the  same  causes  have  been 
effectual  in  producing  the  other  large  lakes  I  am 
unable  to  say,  never  having  had  the  opportunity 
of  studying  their  formation  with  the  same  care. 

The  existence  of  the  numerous  smaller  lakes 
running  north  and  south  in  the  State  of  New 
York,  as  the  Canandaigua,  Seneca,  Cayuga,  etc., 
is  more  easily  accounted  for.  Slow  and  gradual 
as  was  the  process  by  which  all  that  region  was 
lifted  above  the  ocean,  it  was,  nevertheless,  ac- 
companied by  powerful  dislocations  of  the  strati- 
fied deposits,  as  we  shall  see  when  we  examine 
them  with  reference  to  the  local  phenomena  con- 
nected with  them.  To  these  dislocations  of  the 
strata  we  owe  the  transverse  cracks  across  the 
central  part  of  New  York,  which  needed  only  the 
addition  of  the  fresh  water  poured  into  them  by 
the  rains  to  transform  them  into  lakes. 

I  shall  not  attempt  any  account  of  the  differ- 
ences between  the  animals  of  the  Devonian  period 
and  those  of  the  Silurian  period,  because  they 


THE  CARBONIFEROUS  PERIOD.  69 

consist  of  structural  details  difficult  to  present  in 
a  popular  form  and  uninteresting  to  all  but  the 
professional  naturalist.  Suffice  it  to  say,  that, 
though  the  organic  world  had  the  same  general 
character  in  these  two  closely  allied  periods,  yet 
its  representatives  in  each  were  specifically  dis- 
tinct, and  their  differences,  however  slight,  are 
as  constant  and  as  definitely  marked  as  those  be- 
tween more  widely  separated  creations. 

At  the  close  of  the  Devonian  period,  several 
upheavals  occurred  of  great  significance  for  the 
future  history  of  America.  One  in  Ohio  raised 
the  elevated  ground  on  which  Cincinnati  now 
stands ;  another  hill  lifted  its  granite  crest  in 
Missouri,  raising  with  it  an  extensive  tract  of  Si- 
lurian and  Devonian  deposits ;  while  a  smaller 
one,  which  does  not  seem,  however,  to  have  Dis- 
turbed the  beds  about  it  so  powerfully,  broke 
through  in  Arkansas.  At  the  same  time,  eleva- 
tions took  place  toward  the  East,  —  the  first  links, 
few  and  detached,  in  the  great  Alleghany  chain 
which  now  raises  its  rocky  wall  from  New  Eng- 
land to  Alabama. 

In  the  Ohio  hill,  the  granite  did  not  break 
through,  though  the  force  of  the  upheaval  was 
such  as  to  rend  asunder  the  Devonian  deposits, 
for  we  find  them  lying  torn  and  broken  about  the 
base  of  the  hill ;  while  the  Silurian  beds,  which 
should  underlie  them  in  their  natural  position, 


70  THE  FERN  FORESTS  OF 

form  its  centre  and  summit.  This  accounts  for 
the  great  profusion  of  Silurian  organic  remains 
in  that  neighborhood.  Indeed,  there  is  no  local- 
ity which  forces  upon  the  observer  more  strongly 
the  conviction  of  the  profusion  and  richness  of 
the  early  creation.  One  may  actually  collect  the 
remains  of  Silurian  Shells  and  Crustacea  by  cart- 
loads around  the  city  of  Cincinnati.  A  natural- 
ist would  find  it  difficult  to  gather,  along  any 
modern  sea-shore,  even  on  tropical  coasts,  where 
marine  life  is  more  abundant  than  elsewhere,  so 
rich  a  harvest,  in  the  same  time,  as  he  will  bring 
home  from  an  hour's  ramble  in  the  environs  of 
that  city. 

These  elevations  naturally  gave  rise  to  depres- 
sions between  themselves  and  the  land  on  either 
side  of  them,  and  caused  also  so  many  counter- 
slopes  dipping  toward  the  uniform  southern  slope 
already  formed  at  the  north.  Thus  between  the 
several  new  upheavals,  as  well  as  between  them 
all  and  the  land  to  the  north  of  them,  wide  ba- 
sins or  troughs  were  formed,  enclosed  on  the 
south,  west,  and  east  by  low  hills,  (for  these  more 
recent  eruptions  were,  like  all  the  early  upheav- 
als, insignificant  in  height,)  and  bounded  on 
the  north  by  the  more  ancient  shores  of  the  pre- 
ceding ages. 

These  were  the  inland  seas  of  the  Carbonifer- 
ous period.  Here,  again,  we  must  infer  the  sue- 


THE   CARBONIFEROUS  PERIOD.  71 

cessive  stages  of  a  history  which  we  can  read 
only  in  its  results.  Shut  out  from  the  ocean, 
these  shallow  sea-basins  were  gradually  changed 
by  the  rains  to  fresh-water  lakes;  the  lakes,  in 
their  turn,  underwent  a  transformation,  becom- 
ing filled,  in  the  course  of  centuries,  with  the 
materials  worn  away  from  their  shores,  with  the 
debris  of  the  animals  which  lived  and  died  in 
their  waters,  as  well  as  with  the  decaying  matter 
from  aquatic  plants,  till  at  last  they  were  changed 
to  spreading  marshes,  and  on  these  marshes  arose 
the  gigantic  fern-vegetation  of  which  the  first  for- 
ests chiefly  consisted.  Such  are  the  separate 
chapters  in  the  history  of  the  coal-basins  of  Illi- 
nois, Missouri,  Pennsylvania,  New  England,  and 
Nova  Scotia.  First  inland  seas,  then  fresh-water 
lakes,  then  spreading  marshes,  then  gigantic  for- 
ests, and  lastly  vast  storehouses  of  coal  for  the 
human  race. 

Although  coal-beds  are  by  no  means  peculiar 
to  the  Carboniferous  period,  since  such  deposits 
must  be  formed  wherever  the  decay  of  vegetation 
is  going  on  extensively,  yet  it  would  seem  that 
coal-making  was  the  great  work  in  that  age  of 
the  world's  physical  history.  The  atmospheric 
conditions,  so  far  as  we  can  understand  them, 
were  then  especially  favorable  to  this  result. 
Though  the  existence  of  such  an  extensive  ter- 
restrial vegetation  shows  conclusively  that  an  at- 


72  THE  FERN  FORESTS  OF 

mosphere  must  have  been  already  established, 
with  all  the  attendant  phenomena  of  light,  heat, 
air,  moisture,  etc.,  yet  it  is  probable  that  this 
atmosphere  differed  from  ours  in  being  very 
largely  charged  with  carbonic  acid. 

We  should  infer  this  from  the  nature  of  the 
animals  characteristic  of  the  period ;  for,  though 
land-animals  were  introduced,  and  the  organic 
world  was  no  longer  exclusively  marine,  there 
were  as  yet  none  of  the  higher  beings  in  whom 
respiration  is  an  active  process.  In  all  warm- 
blooded animals  the  breathing  is  quick,  requiring 
a  large  proportion  of  oxygen  in  the  surrounding 
air,  and  indicating  by  its  rapidity  the  animation 
of  the  whole  system ;  while  the  slow-breathing, 
cold-blooded  animals  can  live  in  an  air  that  is 
heavily  loaded  with  carbon.  It  is  well  known, 
however,  that,  though  carbon  is  so  deadly  to 
higher  animal  life,  plants  require  it  in  great 
quantities ;  and  it  would  seem  that  one  of  the 
chief  offices  of  the  early  forests  was  to  purify  the  at- 
mosphere of  its  undue  proportion  of  carbonic  acid, 
by  absorbing  the  carbon  into  their  own  substance, 
and  eventually  depositing  it  as  coal  in  the  soil. 

Another  very  important  agent  in  the  process 
of  purifying  the  atmosphere,  and  adapting  it  to 
the  maintenance  of  a  higher  organic  life,  is  found 
in  the  deposits  of  lime.  My  readers  will  excuse 
me,  if  I  introduce  here  a  very  elementary  chemi- 


THE  CARBONIFEROUS  PERIOD.  73 

cal  fact  to  explain  this  statement.  Limestone  is 
carbonate  of  calcium.  Calcium  is  a  metal,  fusi- 
ble as  such,  and,  forming  a  part  of  the  melted 
masses  within  the  earth,  it  was  thrown  out  with 
the  eruptions  of  Plutonic  rocks.  Brought  to  the 
air,  it  would  appropriate  a  certain  amount  of 
oxygen,  and  by  that  process  would  become  oxide 
of  calcium,  in  which  condition  it  combines  very 
readily  with  carbonic  acid.  Thus  it  becomes  car- 
bonate of  lime ;  and  all  lime  deposits  played  an 
important  part  in  establishing  the  atmospheric 
proportions  essential  to  the  existence  of  the 
warm-blooded  animals. 

Such  facts  remind  us  how  far  more  compre- 
hensive the  results  of  science  will  become  when 
the  different  branches  of  scientific  investigation 
are  pursued  in  connection  with  each  other. 
When  chemists  have  brought  their  knowledge 
out  of  their  special  laboratories  into  the  labora- 
tory of  the  world,  where  chemical  combinations 
are  and  have  been  through  all  time  going  on  in 
such  vast  proportions,  —  when  physicists  study 
the  laws  of  moisture,  of  clouds  and  storms,  in 
past  periods  as  well  as  in  the  present,  —  when,  in 
short,  geologists  and  zoologists  are  chemists  and 
physicists,  and  vice  versd,  —  then  we  shall  learn 
more  of  the  changes  the  world  has  undergone 
than  is  possible  now  that  they  are  separately 
studied. 


74  THE  FERN  FORESTS   OF 

It  may  be  asked,  how  any  clew  can  be  found 
to  phenomena  so  evanescent  as  those  of  clouds 
and  moisture.  But  do  we  not  trace  in  the  old 
deposits  the  rain-storms  of  past  times  ?  The 
heavy  drops  of  a  passing  shower,  the  thick,  crowd- 
ed tread  of  a  splashing  rain,  or  the-  small  pin- 
pricks of  a  close  and  fine  one,  —  all  the  story,  in 
short,  of  the  rising  vapors,  the  gathering  clouds, 
the  storms  and  showers  of  ancient  days,  we  find 
recorded  for  us  in  the  fossil  rain-drops  ;  and  when 
we  add  to  this  the  possibility  of  analyzing  the 
chemical  elements  which  have  been  absorbed  into 
the  soil,  but  which  once  made  part  of  the  atmos- 
phere, it  is  not  too  much  to  hope  that  we  shall 
learn  something  hereafter  of  the  meteorology 
even  of  the  earliest  geological  ages. 

The  peculiar  character  of  the  vegetable  tissue 
in  the  trees  of  the  Carboniferous  period,  contain- 
ing, as  it  did,  a  large  supply  of  resin  drawn  from 
the  surrounding  elements,  confirms  the  view  of 
the  atmospheric  conditions  above  stated ;  and 
this  fact,  as  well  as  the  damp,  soggy  soil  in  which 
the  first  forests  must  have  grown,  accounts  for 
the  formation  of  coal  in  greater  quantity  and 
more  combustible  in  quality  than  is  found  in  the 
more  recent  deposits.  But  stately  as  were  those 
fern  forests,  where  plants  which  creep  low  at  our 
feet  to-day,  or  are  known  to  us  chiefly  as  under- 
brush, or  as  rushes  and  grasses  in  swampy 


THE  CARBONIFEROUS  PERIOD.  75 

grounds,  grew  to  the  height  of  lofty  trees,  yet 
the  vegetation  was  of  an  inferior  kind. 

There  has  been  a  gradation  in  time  for  the 
vegetable  as  well  as  the  animal  world.  With  the 
marine  population  of  the  more  ancient  geological 
ages  we  find  nothing  but  sea-weeds,  —  of  great 
variety,  it  is  true,  and,  as  it  would  seem,  from 
some  remains  of  the  marine  Cryptogams  in  early 
times,  of  immense  size,  as  compared  with  modern 
sea-weeds.  But  in  the  Carboniferous  period,  the 
plants,  though  still  requiring  a  soaked  and  marshy 
soil,  were  aerial  or  atmospheric  plants :  they  were 
covered  with  leaves ;  they  breathed ;  their  fructi- 
fication was  like  that  which  now  characterizes  the 
ferns,  the  club-mosses,  and  the  so-called  u  horse- 
tail plants,"  (Equisetacece^)  those  grasses  of  low, 
damp  grounds,  remarkable  for  the  strongly  marked 
articulations  of  the  stem. 

These  were  the  lords  of  the  forests  all  over  the 
world  in  the  Carboniferous  period.  Wherever 
the  Carboniferous  deposits  have  been  traced,  in 
the  United  States,  in  Canada,  in  England,  France, 
Belgium,  Germany,  in  New  Holland,  at  the  Cape 
of  Good  Hope,  and  in  South  America,  the  gen- 
eral aspect  of  the  vegetation  has  been  found  to 
be  the  same,  though  characterized  in  the  different 
localities  by  specific  differences  of  the  same  na- 
ture as  those  by  which  the  various  flora3  are  dis- 
tinguished now  in  different  parts  of  the  same  zone. 


76  THE  FEKN  FORESTS  OF 

For  instance,  the  Temperate  Zone  throughout  the 
world  is  characterized  by  certain  families  of  trees : 
by  Oaks,  Maples,  Beeches,  Birches,  Pines,  etc.; 
but  the  Oaks,  Maples,  Beeches,  Birches,  and  the 
like,  of  the  American  flora  in  that  latitude  differ 
in  species  from  the  corresponding  European  flora. 
So  in  the  Carboniferous  period,  when  more  uni- 
form climatic  conditions  prevailed  throughout  the 
world,  the  character  of  the  vegetation  showed  a 
general  unity  of  structure  everywhere ;  but  it 
was  nevertheless  broken  up  into  distinct  botanical 
provinces  by  specific  differences  of  the  same  kind 
as  those  which  now  give  such  diversity  of  appear- 
ance to  the  vegetation  of  the  Temperate  Zone  in 
Europe  as  compared  with  that  of  America,  or  to 
the  forests  of  South  America  as  compared  with 
those  of  Africa. 

There  can  be  no  doubt  as  to  the  true  nature 
of  the  Carboniferous  forests ;  for  the  structural 
character  of  the  trees  is  as  strongly  marked  in 
their  fossil  remains  as  in  any  living  plants  of  the 
same  character.  We  distinguish  the  Ferns  not 
only  by  the  peculiar  form  of  their  leaves,  often 
perfectly  preserved,  but  also  by  the  fructification 
on  the  lower  surface  of  the  leaves,  and  by  the 
distinct  marks  made  on  the  stem  at  their  point 
of  juncture  with  it.  The  leaf  of  the  Fern,  when 
falling,  leaves  a  scar  on  the  stem  varying  in  shape 
and  size  according  to  the  kind  of  Fern,  so  that 


THE   CARBONIFEROUS  PERIOD.  77 

the  botanist  readily  distinguishes  any  particular 
species  of  Fern  by  this  means,  —  a  birth-mark,  as 
it  were,  by  which  he  detects  the  parentage  of  the 
individual.  Another  indication,  equally  signifi- 
cant, is  found  in  the  tubular  structure  of  the 
wood  in  Ferns.  On  a  vertical  section  of  any 
well-preserved  Fern-trunk  from  the  old  forests 
the  little  tubes  may  be  seen  very  distinctly  run- 
ning up  its  length ;  or,  if  it  be  cut  through  trans- 
versely, they  may  be  traced  by  the  little  pores 
like  dots  on  the  surface.  Trees  of  this  descrip- 
tion are  found  in  the  Carboniferous  marshes, 
standing  erect  and  perfectly  preserved,  with 
trunks  a  foot  and  a  half  in  diameter,  rising  to  a 
height  of  many  feet.  Plants  so  strongly  bitumi- 
nous as  the  Ferns,  when  they  equalled  in  size 
many  of  our  present  forest-trees,  naturally  made 
coal  deposits  of  the  most  combustible  quality. 
It  is  true  that  we  find  the  anthracite  coal  of  the 
same  period  with  comparatively  little  bituminous 
matter ;  but  this  is  where  the  bitumen  has  been 
destroyed  by  the  action  of  the  internal  heat  of 
the  earth. 

Next  to,  the  Ferns,  the  Club-Mosses  (I^ycopo- 
diaceai)  seem  to  have  contributed  most  largely  to 
the  marsh-forests.  They  were  characterized, 
then,  as  now,  by  the  small  size  of  the  leaves 
growing  close  against  the  stem,  so  that  the  stem 
itself,  though  covered  with  leaves,  looks  almost 


78  THE  FERN  FORESTS  OF 

naked,  like  the  stem  of  the  Cactus.  Beside 
these,  there  are  the  tree-like  Equiseta,  in  which 
we  find  the  articulations  on  the  trunk  correspond- 
ing exactly  to  those  now  so  characteristic  of 
those  marsh-grasses  which  are  the  modern  repre- 
sentatives of  this  family  of  plants,  with  cone-like 
fructifications  on  the  summit  of  the  stem. 

I  would  merely  touch  here  upon  a  subject 
which  does  not  belong  to  my  own  branch  of  Nat- 
ural History,  but  is  of  the  greatest  interest  in 
botanical  research,  namely,  the  gradation  of 
plants  in  the  geological  ages,  and  the  combina- 
tion of  characters  •  in  some  of  the  earlier  vege- 
table forms,  corresponding  to  that  already  no- 
ticed in  the  ancient  animal  types.  For  instance, 
in  the  Carboniferous  period  we  have  only  Cryp- 
togams, Ferns,  Lycopodiaceas,  and  Equisetacese. 
In  the  middle  geological  ages,  Coniferae  are  intro- 
duced, the  first  flowering  plant  known  on  earth, 
but  in  which  the  flower  and  fruit  are  very  imper- 
fect as  compared  with  those  of  the  higher  groups. 
The  Coniferas  were  chiefly  represented  in  the 
middle  periods  by  the  Cycadae,  that  peculiar 
group  of  Coniferae,  resembling  Pines  in  their 
structure,  but  recalling  the  Ferns  by  their  exter- 
nal appearance.  The  stem  is  round  and  short, 
its  surface  being  covered  with  scars  similar  to 
those  of  the  Ferns ;  while  on  the  summit  are  ten 
or  more  leaves,  fan-like  and  spreading  when  their 


THE  CARBONIFEROUS  PEEIOD.  79 

growth  is  complete,  but  rolled  up  at  first,  like 
Fern-leaves  before  they  expand.  Their  fruit  re- 
sembles somewhat  the  Pine- Apple. 

The  mode  of  growth  of  the  Coniferae  recalls  a 
feature  of  the  Equisetaceae  also,  in  the  tufts  of 
little  leaves  which  appear  in  whorls  at  regular  in- 
tervals along  the  length  of  the  stem  in  proportion 
as  it  elongates,  reminding  one  of  the  articulations 
on  the  stem  of  the  Equisetaceae.  The  first  cone 
also  appears  on  the  summit  of  the  stem,  like  the 
terminal  cone  in  the  Equisetaceae  and  the  Club- 
Mosses.  Thus  in  certain  types  of  the  vegetable, 
as  well  as  the  animal  creation  of  earlier  times, 
there  was  a  combination  of  features,  afterwards 
divided  and  presented  in  separate  groups.  In 
the  present  times,  no  one  of  these  families  of 
plants  overlaps  the  others,  but  each  has  a  distinct 
individual  character  of  its  own. 

At  the  close  of  the  middle  geological  ages  and 
the  opening  of  the  Tertiary  periods,  the  Monoco- 
tyledons become  abundant,  the  first  plants  with 
flower  and  enclosed  seed,  though  with  no  true 
floral  envelope ;  but  not  until  the  two  last  epochs 
of  the  Tertiary  age  do  we  find  in  any  number  the 
Dicotyledonous  plants,  in  which  flower  and  fruit 
rise  to  their  highest  perfection.  Thus  there  has 
been  a  procession  of  plants,  from  their  earliest  in- 
troduction to  the  present  day,  corresponding  to 
their  botanical  rank  as  they  now  exist,  so  that  the 


80  THE  FERN  FORESTS  OF 

series  of  gradation  in  the  Vegetable  Kingdom,  as 
well  as  the  Animal  Kingdom,  is  the  same,  whether 
founded  upon  succession  in  time  or  upon  com- 
parative structural  rank. 

Some  attempt  has  been  made  to  reproduce  un- 
der an  artistic  form  the  aspect  of  the  world  in 
the  different  geological  ages,  and  to  present  in 
single  connected  pictures  the  animal  and  vege- 
table world  of  each  period.  Professor  F.  Unger, 
of  Vienna,  has  prepared  a  collection  of  fourteen 
such  sketches,  entitled,  "  Tableaux  Physiono- 
miques  de  la  Ve*ge*tation  des  Diverses  Periodes 
du  Monde  Primitif." 

First,  we  have  the  Devonian  shores,  with  spread- 
ing fields  of  sea-weed  and  numbers  of  the  club- 
shaped  Algae  of  gigantic  size.  He  has  ventured, 
also,  to  represent  a  few  trees,  with  scanty  foliage ; 
but  I  believe  their  existence  at  so  early  a  period 
to  be  very  problematical. 

Next  comes  the  Carboniferous  forest,  with  still 
pools  of  water  lying  between  the  Fern-trees, 
which,  much  as  they  affect  damp,  swampy 
grounds,  seem  scarcely  able  to  find  foothold  on 
the  dripping  earth.  Their  trunks,  as  well  as 
those  of  the  Club-Moss  trees  which  make  the 
foreground  of  the  picture,  stand  up  free  from 
any  branches  for  many  feet  above  the  ground, 
giving  one  a  glimpse  between  them  into  the  dim 
recesses  of  this  quiet,  watery  wood,  where  the 


THE   CARBONIFEROUS  PEEIOD.  81 

silence  was  unbroken  by  the  song  of  birds  or  the 
hum  of  insects.  We  shall  find,  it  is  true,  when 
we  give  a  glance  at  the  animals  of  this  time,  that 
certain  insects  made  their  appearance  with  the 
first  terrestrial  vegetation ;  but  they  were  few  in 
number  and  of  a  peculiar  kind,  such  as  thrive 
now  in  low,  wet  lands. 

Upon  this  follow  a  number  of  sketches  intro- 
ducing us  to  the  middle  periods,  where  the  land 
is  higher  and  more  extensive,  covered  chiefly 
with  Pine-forests,  beneath  which  grows  a  thick 
carpet  of  underbrush,  consisting  mostly  of 
Grasses,  Rushes,  and  Ferns.  Here  and  there 
one  of  the  gigantic  reptiles  of  the  time  may  be 
seen  sunning  himself  on  the  shore.  One  of  these 
sketches  shows  us  such  a  creature  hungrily  in- 
specting a  pool  where  Crinoids,  with  their  long 
stems,  large,  closely-coiled  Chambered  Shells, 
and  Brachiopods,  the  Oysters  and  Clams  of  those 
days,  offer  him  a  tempting  repast.  Here  and 
there  a  Pterodactyl,  the  curious  winged  reptile 
of  the  later  middle  periods,  stretches  its  long 
neck  from  the  water,  and  birds  also  begin  to 
make  their  appearance. 

After  these  come  the  Tertiary  periods:  the 
Eocene  first,  where  the  landscape  is  already 
broken  up  by  hills  and  mountains,  clothed  with  a 
varied  vegetation  of  comparatively  modern  char- 
acter. Lily-pads  are  floating  on  the  stream 

4*  p 


82  THE  FERN  FORESTS   OF 

which  makes  the  central  part  of  the  picture; 
large  herds  of  the  Palaeotherium,  the  ancient 
Pachyderm,  reconstructed  with  such  accuracy  by 
Cuvier,  are  feeding  along  its  banks ;  and  a  tall 
bird  of  the  Heron  or  Pelican  kind  stands  watch- 
ing by  the  water's  edge.  In  the  Miocene  the 
vegetation  looks  still  more  familiar,  though  the 
Elephants,  roaming  about  in  regions  of  the  Tem- 
perate Zone,  and  the  huge  Salamanders,  crawling 
out  of  the  water,  remind  us  that  we  are  still  far 
removed  from  present  times.  Lastly,  we  have 
the  ice  period,  with  the  glaciers  coming  down  to 
the  borders  of  a  river  where  large  troops  of  Buf- 
falo are  drinking,  while  on  the  shore  some  Bears 
are  feasting  on  the  remains  of  a  huge  carcass. 

It  is,  however,  with  the  Carboniferous  age  that 
we  have  to  do  at  present,  and  I  will  not  antici- 
pate the  coming  chapters  of  my  story  by  dwelling 
now  oh  the  aspect  of  the  later  periods.  To  re- 
turn, then,  to  the  period  of  the  coal,  it  would 
seem  that  extensive  freshets  frequently  over- 
flowed the  marshes,  and  that  even  after  many 
successive  forests  had  sprung  up  and  decayed 
upon  their  soil,  they  were  still  subject  to  submer- 
gence by  heavy  floods.  These  freshets,  at  certain 
intervals,  are  not  difficult  to  understand,  when 
we  remember,  that,  beside  the  occasional  influx 
of  violent  rains,  the  earth  was  constantly  under- 
going changes  of  level,  and  that  a  subsidence  or 


THE   CAEBONIFEROUS  PEEIOD.  83 

upheaval  in  the  neighborhood  would  disturb  the 
equilibrium  of  the  waters,  causing  them  to  over- 
flow and  pour  over  the  surface  of  the  country, 
thus  inundating  the  marshes  anew. 

That  such  was  the  case  we  can  hardly  doubt, 
after  the  facts  revealed  by  recent  investigations 
of  the  Carboniferous  deposits.  In  some  of  the 
deeper  coal-beds  there  is  a  regular  alternation 
between  layers  of  coal  and  layers  of  sand  or  clay ; 
in  certain  localities,  as  many  as  ten,  twelve,  and 
even  fifteen  coal-beds  have  been  found  alternat- 
ing -with  as  many  deposits  of  clay  or  mud  or 
sand ;  and  in  some  instances,  where  the  trunks 
of  the  trees  are  hollow  and  have  been  left  stand- 
ing erect,  they  are  filled  to  the  brim,  or  to  the 
height  of  the  next  layer  of  deposits,  with  the 
materials  that  have  been  swept  over  them.  Upon 
this  set  of  deposits  comes  a  new  bed  of  coal  with 
the  remains  of  a  new  forest,  and  above  this  again 
a  layer  of  materials  left  by  a  second  freshet,  and 
so  on  through  a  number  of  alternate  strata.  It 
is  evident  from  these  facts  that  there  has  been  a 
succession  of  forests,  one  above  another,  but  that 
in  the  intervals  of  their  growth  great  floods  have 
poured  over  the  marshes,  bringing  with  them  all 
kinds  of  loose  materials,  such  as  sand,  pebbles, 
clay,  mud,  lime,  etc.,  which,  as  the  freshets  sub- 
sided, settled  down  over  the  coal,  filling  not  only 
the  spaces  between  such  trees  as  remained  stand- 


84  THE  FERN  FORESTS   OF 

ing,  but  even  the  hollow  trunks  of  the  trees 
themselves. 

Let  us  give  a  glance  now  at  the  animals  which 
inhabited  the  waters  of  this  period.  In  the  Ra- 
diates we  shall  not  find  great  changes ;  the  three 
classes  are  continued,  though  with  new  represen- 
tatives, and  the  Polyp  Corals  are  increasing,  while 
the  Acalephian  Corals,  the  Rugosa  and  Tabulata, 
are  diminishing.  The  Crinoids  were  still  the 
most  prominent  representatives  of  the  class  of 
Echinoderms,  though  some  resembling  the  Ophi- 
urans  and  Bchinoids  (Sea-Urchins)  began  to 
make  their  appearance.  The  adjoining  wood-cut 
represents  a  characteristic  Crinoid  of  the  Carbon- 
iferous age. 

Among  the  Mollusks,  Bra- 
chiopods  are  still  prominent, 
one  new  genus  among  them,  the 
Productus,  being  very  remark- 
able on  account  of  the  manner 
in  which  one  valve  rises  above 
the  other.  The  following  wood- 
cut represents  such  a  shell, 
looked  at  from  the  side  of  the 
flat  valve,  showing  the  straight 
cut  of  the  line  of  juncture  be- 
tween the  valves  and  the  rising 
curve  of  the  opposite  one, 
which  looks  like  a  hooked  beak  when  seen  in 
profile. 


THE   CARBONIFEROUS   PERIOD. 


85 


Other  species  of  Bivalves 
were  also  introduced,  ap- 
proaching more  nearly  our 
Clams  and  Oysters,  or,  as 
they  are  called  in  scientific 
nomenclature,  the  Lamelli- 
branchiates.  They  differ 
from  the  Brachiopods  chiefly  in  the  higher  char- 
acter of  their  breathing-apparatus  ;  for  they  have 
free  gills,  instead  of  the  net-work  of  vessels  on 
the  lining  skin  which  serves  as  the  organ  of  res- 
piration in  the  Brachiopods.  We  shall  always 
find,  that,  in  proportion  as  the  functions  are  dis- 
tinct, and,  as  it  were,  individualized  by  having 
special  organs  appropriated  to  them,  animals  rise 
in  the  scale  of  structure.  The  next  class  of  Mol- 
lusks,  the  Gasteropods,  or  Univalves,  with  spiral 
shells,  were  numerous,  but,  from  their  brittle 
character,  are  seldom  found  in  a  good  state  of 
preservation. 

The  Chambered  Shells,  or  the  Cephalopods, 
represented  chiefly  in  the  earlier  periods  by  the 
straight  Orthoceratites  de- 
scribed in  a  previous  article, 
are  now  curled  in  a  close 
coil,  and  the  internal  struc- 
ture of  their  chambers  has 
become  more  complicated. 
The  subjoined  wood-cut  rep- 


86  THE  FERN  FORESTS  OF 

resents  a  characteristic  Chambered  Shell  of  the 
Carboniferous  age.  Goniatites  is  the  scientific 
name  of  these  later  forms.  If  we  had  looked  for 
them  in  the  Devonian  period,  we  should  have 
found  many  with  looser  coils  than  these,  and 
some  only  slightly  curved  in  the  shape  of  a  horn. 
These,  as  well  as  the  perfectly  straight  forms, 
still  exist  in  the  coal  period,  but  the  Goniatites 
with  close  whorls  are  the  more  numerous  and 
more  characteristic. 

The  Articulates  have  gained  their  missing  class 
since  the  close  of  the  Devonian  period,  for  In- 
sects have  come  in,  and  that  division  of  the  Ani- 
mal Kingdom  is  therefore  complete,  and  repre- 
sented by  three  classes,  as  it  is  at  present.  Of 
the  Worms  little  can  be  said ;  their  traces  are 
found  as  before,  but  they  are  very  imperfectly 
preserved.  There  are  still  Trilobites,  but  they 
are  very  few  in  number,  and 
other  groups  of  Crustacea 
have  been  added. 

One  of  the  most  prominent 
of  these  new  types  bears  a 
striking  resemblance  to  the 
Horse-Shoe  Crab  of  present 
times.  I  here  present  one  of 
our  common  Horse-Shoe  Crabs 
above  one  of  these  old-world 
Crustaceans,  and  it  will  be 


THE   CARBONIFEROUS  PERIOD.  87 

seen,  that  while  the  latter 
preserves  some  of  the  Trilo- 
bitic  characters,  such  as  the 
marked  articulations  on  the 
posterior  part  of  the  body 
and  their  division  into  three 
lobes,  yet,  in  the  prominence 
of  its  anterior  shield,  its 
more  elongated  form,  and 
tapering  extremity,  it  resembles  its  modern  rep- 
resentative. In  some  of  them,  however,  there  is 
no  such  sharp  point  as  is  here  figured,  and  the 
body  terminates  bluntly.  There  were  a  large 
number  of  these  Entomostraca  in  the  Carbonif- 
erous period,  a  group  which  is  chiefly  represented 
among  living  Crustacea  by  an  exceedingly  mi- 
nute kind  of  Shrimp ;  but  in  those  days  they 
were  of  the  size  of  our  Crabs  and  Lobsters,  or 
even  larger,  and  the  Horse-Shoe  Crab  still  main- 
tains their  claim 
to  a  place  among 
the  larger  and 
more  conspicuous 
members  of  the 
class. 

The  Insects 
were  few,  and, 
as  I  have  said 
above,  of  a  kind 


88  THE  FEEN  FOEESTS   OF 

which  seeks  a  moist  atmosphere,  or  whose  larvae 
live  altogether  in  water.  They  are  not  usually 
well  preserved,  as  will  be  seen  from  the  broken 
character  of  the  one  here  represented,  although 
the  wood-cut  is  made  from  a  better  specimen 
than  is  often  found.  We  have,  however,  re- 
mains enough  to  establish  unquestionably  the 
fact  of  their  existence  in  the  Carboniferous  pe- 
riod, and  to  show  us  that  the  type  of  Articulates 
was  already  represented  by  all  its  classes. 

Not  so  with  the  Vertebrates.  Fishes  abound, 
but  their  class  still  consists,  as  before,  of  the  Ga- 
noids, those  fishes  of  the  earlier  periods  built  on 
the  Gar-Pike  and  Sturgeon  pattern,  and  the  Sela- 
chians, represented  now  by  Sharks  and  Skates. 
In  the  Carboniferous  period  we  begin  to  find  per- 
fectly preserved  specimens  of  the  Ganoids,  and 

the  adjoining 
wood-cut  rep- 
resents such  a 
one.  Of  the 
old  type  of 
Selachians  we 
have  again  one 

lingering  representative  in  our  own  times  to  give 
us  the  clew  to  its  ancestors,  —  as  the  Gar-Pike 
explains  the  old  Ganoids,  and  the  Chambered 
Nautilus  helps  us  to  understand  the  Chambered 
Shells  of  past  times.  The  so-called  Port-Jackson 


THE  CARBONIFEROUS  PERIOD.  89 

Shark  has  features  which  were  very  character- 
istic of  the  Carboniferous  Sharks  and  are  lost  in 
the  modern  ones,  so  that  it  affords  us  a  sort  of 
link,  as  it  were,  and  a  measure  of  comparison, 
between  those  now  living  and  the  more  ancient 
forms.  It  is  an  interesting  fact  that  this  only 
living  representative  of  the  Carboniferous  Shark 
should  be  found  in  New  Holland,  because  it  is 
there,  in  that  isolated  continent,  left  apart,  as  it 
would  seem,  for  a  special  purpose,  that  we  find 
reproduced  for  us  most  fully  the  character  of  the 
Animal  Kingdom  in  earlier  creations. 

The  first  Mammalia  in  the  world  were  pouched 
animals,  having  that  extraordinary  attachment 
to  the  mother  after  birth  which  characterizes  the 
Kangaroo.  In  New  Holland  almost  all  the  Mam 
malia  are  pouched,  and  have  also  the  imperfect 
organization  of  the  brain,  as  compared  with  the 
other  Mammalia,  which  accompanies  that  pecu- 
liar structural  feature ;  and  although  the  Amer- 
ican Opossum  makes  an  exception  to  the  rule, 
it  is  nevertheless  true  that  this  type  of  the  Ani- 
mal Kingdom  is  now  confined  almost  exclusively 
to  New  Holland.  Whether  this  living  picture  of 
old  creations  in  modern  garb  was  meant  to  be 
educational  for  man  or  not,  it  is  at  least  well 
that  we  should  take  advantage  of  it  in  learning 
all  it  has  to  teach  us  of  the  relations  between  the 
organic  world  of  past  and  present  times. 


THE  FERN  FORESTS  OF 


There  were  a  great  variety  of  the  Selachians 
in  the  Carboniferous  period.  The  wood-cuts  be- 
low represent  a  tooth  and  a  spine  from  one  of  the 


most  characteristic  groups,  but  I 
have  not  thought  it  worth  while 
to  enumerate  or  to  figure  others 
here,  for  there  are  no  perfect  spe- 
cimens, and  their  structural  dif- 
ferences consist  chiefly  in  the 
various  form  and  appearance  of 
the  teeth,  scales,  and  spines,  and  would  be  unin- 
teresting to  most  of  my  readers.  I  would  refer 
the  more  scientific  ones,  who  may  care  to  know 
something  of  these  details,  to  my  investigations 
on  Fossil  Fishes,  published  many  -  years  since 
under  the  title  of  "  Recherches  sur  les  Poissons 
Fossiles." 

Although  the  Vertebrate  division  of  the  Ani- 
mal Kingdom  still  waited  for  its  higher  classes, 
yet  it  had  received  one  important  addition  since 


THE  CAKBONIFEROUS  PERIOD.  91 

the  Silurian  and  Devonian  periods.  The  Car- 
boniferous marshes  were  not  without  their  rep- 
tilian inhabitants ;  but  they  were  Reptiles  of  the 
lowest  class,  the  so-called  Amphibians,  those 
which  are  hatched  from  the  egg  in  an  immature 
condition,  undergoing  metamorphosis  after  birth. 
They  have  no  hard  scales,  and  lay  a  large  num- 
ber of  eggs.  I  am  unable  to  present  any  figure 
of  one  of  these  ancient  Reptiles,  as  they  are 
found  in  so  imperfect  a  state  of  preservation  that 
no  plates  have  been  made  from  them.  I  would 
add,  in  connection  with  this  subject,  that  I  believe 
a  large  number  of  animals  found  in  the  Carbon- 
iferous deposits,  and  referred  to  the  class  of  Rep- 
tiles, to  be  Fishes  allied  to  Saurians. 

Before  leaving  the  Carboniferous  period,  let  us 
see  what  territory  the  United  States  has  con- 
quered from  the  Ocean  during  that  time.  All  its 
central  portion,  from  Canada  to  Alabama,  and 
from  Western  Iowa,  Missouri,  and  Arkansas  to 
Eastern  Virginia,  was  raised  above  the  water. 
But  as  yet  the  Alleghanies  and  the  Rocky  Moun- 
tains did  not  exist ;  a  great  gulf  ran  up  to  the 
mouth  of  the  Ohio,  for  the  Mississippi  had  not 
yet  accumulated  the  soil  for  the  fertile  valley 
through  which  it  was  to  take  its  southern  course  ; 
the  Coral-Builders  had  still  their  work  to  do  in 
constructing  the  peninsula  of  Florida ;  and,  in- 
deed, all  the  borders  of  the  continent  of  North 


92  THE  FERN  FORESTS  OF 

America,  as  well  as  a  large  part  of  its  Western 
territory,  were  still  to  be  added.  But  although 
its  central  portion  held  its  ground  and  was  never 
submerged  again,  yet  the  continent  was  slowly 
subsiding  during  the  middle  geological  periods, 
so  that,  instead  of  enlarging  gradually  by  the  in- 
crease of  deposits,  its  limits  remained  much  the 
same. 

This  accounts  for  the  very  scanty  traces  to  be 
found  in  America  of  the  secondary  deposits  ;  for 
the  Permian,  Triassic,  and  Jurassic  beds,  instead 
of  being  raised  to  form  successive  shores,  along 
which  their  deposits  could  be  accumulated  in  reg- 
ular sequence,  as  had  been  the  case  with  the 
Azoic,  Silurian,  and  Devonian  deposits  in  the 
northern  part  of  the  United  States,  were  con- 
stantly sinking,  so  that  the  Triassic  settled  above 
the  Permian,  the  Jurassic  above  the  Triassic,  and 
so  on,  each  set  of  strata  thus  covering  over  and 
concealing  the  preceding  one.  Though  we  find 
the  stratified  rocks  of  these  periods  cropping  out 
here  and  there,  where  some  violent  disturbance 
or  the  abrading  action  of  water  has  torn  asunder 
or  worn  away  the  overlying  strata,  yet  we  never 
find  them  consecutively  over  any  extensive  re- 
gion ;  and  it  is  not  till  the  Cretaceous  and  earlier 
Tertiary  periods  that  we  find  again  a  regular  suc- 
cession of  deposits  around  the  shores  of  the  con- 
tinent, marking  its  present  outlines.  It  is,  then, 


THE  CARBONIFEROUS  PERIOD.  93 

in  Europe,  where  the  sequence  of  their  beds  is 
most  complete,  that  we  must  seek  to  decipher  the 
history  of  the  middle  geological  ages ;  and  there- 
fore, when  I  meet  my  readers  again,  it  will  be  in 
the  Old  World  of  civilization,  though  more  recent 
in  its  physical  features  than  the  one  we  leave. 


IV. 

MOUNTAINS   AND  THEIR  ORIGIN. 

A  CHAPTER  on  mountains  will  not  be  an 
inappropriate  introduction  to  that  part  of 
the  world's  history  on  which  we  are  now  enter- 
ing, when  the  great  inequalities  of  the  earth's 
surface  began  to  make  their  appearance  ;  and  be- 
fore giving  any  special  account  of  the  geological 
succession  in  Europe,  I  will  say  something  of  the 
formation  of  mountains  in  general,  and  of  the 
men  whose  investigations  first  gave  us  the  clew 
to  the  intricacies  of  their  structure.  It  has  been 
the  work  of  the  nineteenth  century  to  decipher 
the  history  of  the  mountains,  to  smooth  out  these 
wrinkles  in  the  crust  of  the  earth,  to  show  that 
there  was  a  time  when  they  did  not  exist,  to  de- 
cide at  least  comparatively  upon  their  age,  and  to 
detect  the  forces  which  have  produced  them. 

But  while  I  speak  of  the  reconstructive  labors 
of  the  geologist  with  so  much  confidence,  because 
to  my  mind  they  reveal  an  intelligible  coherence 
in  the  whole  physical  history  of  the  world,  yet  I 
am  well  aware  that  there  are  many  and  wide  gaps 


MOUNTAINS  AND  THEIE  ORIGIN.  95 

in  our  knowledge  to  be  filled  up.  All  the  at- 
tempts to  represent  the  appearance  of  the  earth 
in  past  periods  by  means  of  geological  maps  are, 
of  course,  but  approximations  of  the  truth,  and 
will  compare  with  those  of  future  times  when 
the  phenomena  are  better  understood,  much  as 
our  present  geographical  maps,  the  result  of  re- 
peated surveys  and  of  the  most  accurate  meas- 
urements, compare  with  those  of  the  ancients. 

Homer's  world  was  a  flat  expanse,  surrounded 
by  ocean,  of  which  Greece  was  the  centre.  Asia 
Minor,  the  JBgean  Islands,  Egypt,  part  of  Italy 
and  Sicily,  the  Mediterranean  and  the  Black  Sea 
filled  out  and  completed  his  map. 

Hecatseus,  the  Greek  historian  and  geographer, 
who  lived  more  than  five  hundred  years  before 
Christ,  had  not  enlarged  it  much.  He  was,  to  be 
sure,  a  voyager  on  the  Mediterranean,  and  had 
an  idea  of  the  extent  of  Italy.  Acquaintance 
with  Phoenician  merchants  also  had  enlarged  his 
knowledge  of  the  world ;  Sardinia,  Corsica,  and 
Spain  were  known  to  him,  and  he  was  familiar 
with  the  Black  and  Red  Seas;  though  an  in- 
dentation on  his  map  in  the  neighborhood  of  the 
Caspian  would  seem  to  indicate  that  he  was 
aware  of  the  existence  of  this  sea  also,  it  is  not 
otherwise  marked. 

Herodotus  makes  a  considerable  advance  be- 
yond his  predecessors:  the  Caspian  Sea  has  a 


96  MOUNTAINS  AND  THEIR  ORIGIN. 

place  on  his  map ;  Asia  is  sketched  out,  includ- 
ing the  Persian  Gulf,  with  the  large  rivers  pour- 
ing into  it;  and  the  course  of  the  Ganges  is 
traced,  though  he  makes  it  flow  east  and  empty 
into  the  Pacific,  instead  of  turning  southward 
and  emptying  into  the  Indian  Ocean. 

Eratosthenes,  two  centuries  before  Christ,  is 
the  first  geographer  who  makes  some  attempt  to 
determine  the  trend  to  the  land  and  water,  pre- 
senting a  suggestion  that  the  earth  is  broader  in 
one  direction  than  in  the  other.  In  his  map  he 
adds  also  the  geographical  results  derived  from 
the  expeditions  of  Alexander  the  Great. 

Ptolemy,  who  flourished  in  Alexandria  in  the 
reign  of  Hadrian,  is  the  next  geographer  of  emi- 
nence, and  he  shows  us  something  of  Africa ;  for, 
in  his  time,  the  Phoenicians,  in  their  commercial 
expeditions,  had  sailed  far  to  the  south,  had 
reached  the  termination  of  Africa,  with  ocean 
lying  all  around  it,  and  had  seen  the  sun  to  the 
north  of  them.  This  last  assertion,  however, 
Ptolemy  does  not  credit,  and  he  is  as  sceptical  of 
the  open  ocean  surrounding  the  extremity  of  Af- 
rica as  modern  geographers  and  explorers  have 
been  of  the  existence  of  Kane's  open  Arctic  Sea. 
He  believes  that  what  the  Phoenician  traders  took 
to  be  the  broad  ocean  must  be  part  of  an  inland 
sea,  corresponding  to  the  Mediteranean,  with 
which  he  was  so  familiar.  His  map  includes 


MOUNTAINS  AND  THEIR  ORIGIN.  97 

also  England,  Ireland,  and  Scotland ;  and  his 
Ultima  Thule  is,  no  doubt,  the  Hebrides  of  our 
days. 

Our  present  notions  of  the  past  periods  of  the 
world's  history  probably  bear  about  the  same  re- 
lation to  the  truth  that  these  ancient  geographi- 
cal maps  bear  to  the  modern  ones.  But  this 
should  not  discourage  us,  for,  after  all,  those 
maps  were  in  the  main  true  as  far  as  they  went ; 
and  as  the  ancient  geographers  were  laying  the 
foundation  for  all  our  modern  knowledge  of  the 
present  conformation  of  the  globe,  so  are  the 
geologists  of  the  nineteenth  century  preparing 
the  ground  for  future  investigators,  whose  work 
will  be  as  far  in  advance  of  theirs  as  are  the  de- 
lineations of  Carl  Ritter,  the  great  master  of 
physical  geography  in  our  age,  in  advance  of  the 
map  drawn  by  the  old  Alexandrian  geographer. 
We  shall  have  our  geological  explorers  and  dis- 
coverers in  the  lands  and  seas  of  past  times,  as 
we  have  had  in  those  of  the  present,  —  our  Co- 
lumbuses,  our  Captain  Cooks,  our  Livingstones 
in  geology,  as  we  have  had  in  geography.  There 
are  undiscovered  continents  and  rivers  and  in- 
land seas  in  the  past  world  to  exercise  the  inge- 
nuity, courage,  and  perseverance  of  men,  after 
they  shall  have  solved  all  the  problems,  sounded 
all  the  depths,  and  scaled  all  the  heights  of  the 
present  surface  of  the  earth. 

5  o 


98  MOUNTAINS  AND  THEIR  OEIGIN. 

What  has  been  done  thus  far  is  chiefly  to  clas- 
sify the  inequalities  of  the  earth's  surface,  and  to 
detect  the  different  causes  which  have  produced 
them.  Foldings  of  the  earth's  crust,  low  hills, 
extensive  plains,  mountain-chains  and  narrow 
valleys,  broad  table-lands  and  wide  valleys,  local 
chimneys  or  volcanoes,  river-beds,  lake-basins,  in- 
land seas,  —  such  are  some  of  the  phenomena 
which,  disconnected  as  they  seem  at  first  glance, 
have  nevertheless  been  brought  under  certain 
principles,  and  explained  according  to  definite 
physical  laws. 

Formerly  men  looked  upon  the  earth  as  a  unit 
in  time,  as  the  result  of  one  creative  act,  with  all 
its  outlines  established  from  the  beginning.  It 
has  been  the  work  of  modern  science  to  show 
that  its  inequalities  are  not  contemporaneous  or 
simultaneous,  but  successive,  including  a  law  of 
growth,  —  that  heat  and  cold,  and  the  consequent 
expansion  and  contraction  of  its  crust,  have  pro- 
duced wrinkles  and  folds  upon  the  surface,  while 
constant  oscillations,  changes  of  level  which  are 
even  now  going  on,  have  modified  its  conforma- 
tion, and  moulded  its  general  outline  through 
successive  ages. 

In  thinking  of  the  formation  of  the  globe,  we 
must  at  once  free  ourselves  from  the  erroneous 
impression  that  the  crust  of  the  earth  is  a  solid, 
steadfast  foundation.  So  far  from  being  immov- 


MOUNTAINS  AND  THEIR   ORIGIN.  99 

able,  it  has  been  constantly  heaving  and  falling ; 
and  if  we  are  not  impressed  by  its  oscillations,  it 
is  because  they  are  not  so  regular  or  so  evident 
to  our  senses  as  the  rise  and  fall  of  the  sea.  The 
disturbances  of  the  ocean,  and  the  periodical 
advance  and  retreat  of  its  tides,  are  known  to 
our  daily  experience ;  we  have  seen  it  tossed  into 
great  billows  by  storms,  or  placid  as  a  lake  when 
undisturbed.  But  the  crust  of  the  earth  also  has 
had  its  storms,  to  which  the  tempests  of  the  sea 
are  as  nothing,  —  which  have  thrown  up  moun- 
tain waves  twenty  thousand  feet  high,  and  fixed 
them  where  they  stand,  perpetual  memorials  of 
the  convulsions  that  upheaved  them.  Conceive 
an  ocean  wave  that  should  roll  up  for  twenty 
thousand  feet,  and  be  petrified  at  its  greatest 
height :  the  mountains  are  but  the  gigantic  waves 
raised  on  the  surface  of  the  land  by  the  geologi- 
cal tempests  of  past  times.  Besides  these  sudden 
storms  of  the  earth's  surface,  there  have  been  its 
gradual  upheavals  and  depressions,  going  on  now 
as  steadily  as  ever,  and  which  may  be  compared 
to  the  regular  action  of  the  tides.  These,  also, 
have  had  their  share  in  determining  the  outlines 
of  the  continents,  the  height  of  the  lands,  and 
the  depth  of  the  seas. 

Leaving  aside  the  more  general  phenomena,  let 
us  look  now  at  the  formation  of  mountains  espe- 
cially. I  have  stated  in  a  previous  article  that 


100  MOUNTAINS  AND  THEIR  ORIGIN. 

the  relative  position  of  the  stratified  and  unstra- 
tified  rocks  gives  us  the  key  to  their  comparative 
age.  To  explain  this  I  must  enter  into  some  de- 
tails respecting  the  arrangement  of  stratified  de- 
posits on  mountain-slopes'  and  in  mountain-chains, 
taking  merely  theoretical  cases,  however,  to  illus- 
trate phenomena  which  we  shall  meet  with  re- 
peatedly in  actual  facts,  when  studying  special 
geological  formations. 

We  have,  for  in- 
stance, in  Figure  1,  a 
central  granite  moun- 
tain, with  a  succession 
of  stratified  beds  slop- 
ing against  its  sides, 

while  at  its  base  are  deposited  a  number  of  hori- 
zontal beds  which  have  evidently  never  been  dis- 
turbed from  the  position  in  which  they  were  orig- 
inally accumulated.  The  reader  will  at  once 
perceive  the  method  by  which  the  geologist  de- 
cides upon  the  age  of  such  a  mountain.  He 
finds  the  strata  upon  its  slopes  in  regular  super- 
position, the  uppermost  belonging,  we  will  sup- 
pose, to  the  Triassic  period ;  at  its  base  he  finds 
undisturbed  horizontal  deposits,  also  in  regular 
superposition,  belonging  to  the  Jurassic  and  Cre- 
taceous periods.  Therefore,  he  argues,  this 
mountain  must  have  been  uplifted  after  the  Tri- 
assic and  all  preceding  deposits  were  formed, 


MOUNTAINS  AND  THEIR   ORIGIN.  101 

since  it  has  broken  its  way  through  them,  and 
forced  them  out  of  their  natural  position ;  and  it 
must  have  been  previous  to  the  Jurassic  and  Cre- 
taceous deposits,  since  they  have  been  accumu- 
lated peacefully  at  its  base,  and  have  undergone 
no  such  perturbations. 

The  task  of  the  geologist  would  be  an  easy 
one,  if  all  the  problems  he  has  to  deal  with  were 
as  simple  as  the  case  I  have  presented  here ;  but 
the  most  cursory  glance  at  the  intricacies  of 
mountain-structure  will  show  us  how  difficult  it 
is  to  trace  the  connection  between  the  phenom- 
ena. We  must  not  form  an  idea  of  ancient 
mountain-upheavals  from  existing  active  volca- 
noes, although  the  causes  which  produced  them 
were,  in  a  somewhat  modified  sense,  the  same. 
Our  present  volcanic  mountains  are  only  chim- 
neys, or  narrow  tunnels,  as  it  were,  pierced  in 
the  thickness  of  the  earth's  surface,  through 
which  the  molten  lava  pours  out,  flowing  over 
the  edges  and  down  the  sides  and  hardening 
upon  the  slopes,  so  as  to  form  conical  elevations. 
The  mountain-ranges  upheaved  by  ancient  erup- 
tions, on  the  contrary,  are  folds  of  the  earth's 
surface,  produced  by  the  cooling  of  a  compara- 
tively thin  crust  upon  a  hot  mass.  The  first 
effect  of  this  cooling  process  would  be  to  cause 
contractions  ;  the  next,  to  produce  corresponding 
protrusions,  —  for,  wherever  such  a  shrinking  and 


102  MOUNTAINS  AND  THEIR   ORIGIN. 

subsidence  of  the  crust  occurred,  the  consequent 
pressure  upon  the  melted  materials  beneath  must 
displace  them  and  force  them  upward.  While 
the  crust  continued  so  thin  that  these  results 
could  go  on  without  very  violent  dislocations,  — 
the  materials  within  easily  finding  an  outlet,  if 
displaced,  or  merely  lifting  the  surface  without 
breaking  through  it,  —  the  effect  would  be  mode- 
rate elevations  divided  by  corresponding  depres- 
sions. We  have  seen  this  kind  of  action,  during 
the  earlier  geological  epochs,  in  the  upheaval  of 
the  low  hills  in  the  United  States,  leading  to  the 
formation  of  the  coal-basins. 

On  our  return  to  the  study  of  the  American 
continent,  we  shall  find  in  the  Alleghany  chain, 
occurring  at  a  later  period,  between  the  Carbon- 
iferous and  Triassic  epochs,  a  good  illustration 
of  the  same  kind  of  phenomena,  though  the  ac- 
tion of  the  Plutonic  agents  was  then  much  more 
powerful,  owing  to  the  greater  thickness  of  the 
crust  and  the  consequent  increase  of  resistance. 
The  folds  forced  upward  in  this  chain  by  the  sub- 
sidence of  the  surface  are  higher  than  any  pre- 
ceding elevations ;  but  they  are  nevertheless  a 
succession  of  parallel  folds  divided  by  correspond- 
ing depressions,  nor  does  it  seem  that  the  dis- 
placement of  the  materials  within  the  crust  was 
so  violent  as  to  fracture  it  extensively. 

Even   so  late  as  the  formation  of  the   Jura 


MOUNTAINS  AND   THEIR   ORIGIN.  103 

mountains,  between  the  Jurassic  and  Cretaceous 
periods,  the  character  of  the  upheaval  is  the 
same,  though  there  are  more  cracks  at  right 
angles  with  the  general  trend  of  the  chain,  and 
here  and  there  the  masses  below  have  broken 
through.  But  the  chain,  as  a  whole,  consists  of 
a  succession  of  parallel  folds,  forming  long  domes 
or  arches,  divided  by  longitudinal  valleys.  The 
valleys  represent  the  subsidences  of  the  crust; 
the  domes  are  the  corresponding  protrusions  re- 
sulting from  these  subsidences.  The  lines  of 
gentle  undulation  in  this  chain,  so  striking  in 
contrast  to  the  rugged  and  abrupt  character  of 
the  Alps  immediately  opposite,  are  the  result  of 
this  mode  of  formation. 

After  the  crust  of  the  earth  had  grown  so 
thick,  as  it  was,  for  instance,  in  the  later  Tertiary 
periods,  when  the  AJps  were  uplifted,  such  an 
eruption  could  take  place  only  through  the 
agency  of  an  immense  force,  and  the  extent  of 
the  fracture  would  be  in  proportion  to  the  resist- 
ance opposed.  It  is  hardly  to  be  doubted,  from 
the  geological  evidence  already  collected,  that 
the  whole  mountain-range  from  Western  Europe 
through  the  continent  of  Asia,  including  the 
Alps,  the  Caucasus,  and  the  Himalayas,  was 
raised  at  the  same  time.  A  convulsion  that  thus 
made  a  gigantic  rent  across  two  continents,  giv- 
ing egress  to  three  such  mountain-ranges,  must 


104  MOUNTAINS  AND  THEIR   ORIGIN. 

have  been  accompanied  by  a  thousand  fractures 
and  breaks  in  contrary  directions.  Such  a  press- 
ure along  so  extensive  a  tract  could  not  be  equal 
everywhere ;  the  various  thicknesses  of  the  crust, 
the  greater  or  less  flexibility  of  the  deposits,  the 
direction  of  the  pressure,  would  give  rise  to  an 
infinite  variety  in  the  results ;  accordingly,  in- 
stead of  the  long,  even  arches,  such  as  character- 
ize the  earlier  upheavals  of  the  Alleghanies  and 
the  Jura,  there  are  violent  dislocations  of  the  sur- 
face, cracks,  rents,  and  fissures  in  all  directions, 
transverse  to  the  general  trend  of  the  upheaval, 
as  well  as  parallel  with  it. 

Leaving  aside  for  the  moment  the  more  baffling 
and  intricate  problems  of  the  later  mountain-for- 
mations, I  will  first  endeavor  to  explain  the  sim- 
pler phenomena  of  the  earlier  upheavals. 

Suppose  that  the  melted  materials  within  the 
earth  are  forced  up  against  a  mass  of  stratified 
deposits,  the  direction  of  the  pressure  being  per- 
fectly yertical,  as  represented  in 
Figure  2.  Such  a  pressure,  if 
not  too  violent,  would  simply  lift 
the  strata  out  of  their  horizontal 
position  into  an  arch  or  dome, 
(as  in  Figure  3,)  and  if  contin-  1<ig-li 

ued  or  repeated  in  immediate  sequence,  it  would 
produce  a  number  of  such  domes,  like  long  bil- 
lows following  each  other,  such  as  we  have  in  the 


MOUNTAINS  AND  THEIR   ORIGIN.  105 

Jura.  But  though  this  is  the 
prevailing  character  of  the 
range,  there  are  many  instan- 
ces even  here  where  an  une- 
3.  qual  pressure  has  caused  a 

rent  at  right  angles  with  the  general  direction  of 
the  upheaval ;  and  one  may  trace  the  action  of 
this  unequal  pressure,  from  the  unbroken  arch, 
where  it  has  simply  lifted  the  surface  into  a 
dome,  to  the  granite  crest,  where  the  melted  rock 
has  forced  its  way  out  and  crystallized  between 
the  broken  beds  that  rest  against  its  slopes. 

In  other  instances,  the  upper  beds  alone  may 
nave  been  cracked,  while  the  continuity  of  the 
lower  ones  remains  unbroken.  In  this  case  we 
have  a  longitudinal  valley  on  the  top  of  a  moun- 
tain-range, lying  between  the  two  sides  of  the 

broken  arch  (as  in 
Figure  4).  Suppose, 
now,  that  there  are 
also  transverse  cracks 
Fi  4  across  such  a  longitu- 

dinal split,  we  have 

then  a  longitudinal  valley  with  transverse  valleys 
opening  into  it.  There  are  many  instances  of 
this  in  the  Alleghanies  and  in  the  Jura.  Some- 
times such  transverse  valleys  are  cut  straight 
across,  so  that  their  openings  face  each  other ; 
but  often  the  cracks  have  taken  plaice  at  different 

5* 


106  MOUNTAINS  AND   THEIE   ORIGIN. 

points  on  the  opposite  sides,  so  that,  in  travelling 
through  such  a  transverse  valley,  you  turn  to  the 
right  or  left,  as  the  case  may  be,  where  it  enters 
the  longitudinal  valley,  and  follow  that  till  you 
come  to  another  transverse  valley  opening  into  it 
from  the  opposite  side,  through  which  you  make 
your  way  out,  thus  crossing  the  chain  in  a  zigzag 
course  (as  in  Fig- 
ure 5).  Such  val- 
leys are  often  much 
narrower  at  some 
points  than  at  oth- 
ers. There  are 
even  places  in  the 

1  Fig.  5.  , 

Jura  where  a  rent 

in  the  chain  begins  with  a  mere  crack,  —  a  slit 
but  just  wide  enough  to  admit  the  blade  of  a 
knife ;  follow  it  for  a  while,  and  you  may  find 
it  spreading  gradually  into  a  wider  chasm,  and 
finally  expanding  into  a  valley  perhaps  half  a  mile 
wide,  or  even  wider. 

By  means  of  such  cracks,  rivers  often  pass 
through  lofty  mountain-chains,  and  when  we 
come  to  the  investigation  of  the  glacial  phenom- 
ena connected  with  the  course  of  the  Rhone,  we 
shall  find  that  river  following  the  longitudinal 
valley  which  separates  the  northern  and  southern 
parts  of  the  chain  of  the  Alps  till  it  comes  to 
Martigny,  where  it  takes  a  sharp  turn  to  the 


MOUNTAINS  AND  THEIR  OEIGIN.  107 

right  through  a  transverse  crack,  flowing  north- 
ward between  walls  fourteen  thousand  feet  high, 
till  it  enters  the  Lake  of  Geneva,  through  which 
it  passes,  issuing  at  the  other  end,  where  it  takes 
a  southern  direction.  For  a  long  time  moun- 
tains were  supposed  to  be  the  limitations  of  riv- 
ers, and  old  maps  represent  them  always  as  flow- 
ing along  the  valleys  without  ever  passing  through 
the  mountain-chains  that  divide  them ;  but  geol- 
ogy is  fast  correcting  the  errors  of  geography, 
and  a  map  which  represents  merely  the  external 
features  of  a  country,  without  reference  to  their 
structural  relations,  is  no  longer  of  any  scientific 
value. 

It  is  not,  however,  by  rents  in  mountain-chains 
alone,  or  by  depressions  between  them,  that  val- 
leys are  produced ;  they  are  often  due  to  the  un- 
equal hardness  of  the  beds  raised,  and  to  their 
greater  or  less  liability  to  be  worn  away  and  dis- 
integrated by  the  action  of  the  rains.  This  ine- 
quality in  the  hardness  of  the  rocks  forming  a 
mountain-range,  not  only  adds  very  much  to  the 
picturesqueness  of  outline,  but  also  renders  the 
landscape  more  varied  through  the  greater  or  less 
fertility  of  the  soil.  On  the  hard  rocks,  where 
little  soil  can  gather,  there  are  only  pines,  or  a 
low,  dwarfed  growth ;  but  on  the  rocks  of  softer 
materials,  more  easily  acted  upon  by  the  rain,  a 
richer  soil  gathers,  and  there,  in  the  midst  of 


108  MOUNTAINS  AND  THEIR   ORIGIN. 

mountain-scenery,  may  be  found  the  most  fertile 
growth,  the  richest  pasturage,  the  brightest  flow- 
ers. Where  such  a  patch  of  arable  soil  has  a 
southern  exposure  on  a  mountain-side,  we  may 
have  a  most  fertile  vegetation  at  a  great  height, 
and  surrounded  by  the  dark  pine-forests.  Many 
of  the  pastures  on  the  Alps,  to  which  from  height 
to  height  the  shepherds  ascend  with  their  flocks 
in  the  summer,  —  seeking  the  higher  ones  as  the 
lower  become  dry  and  exhausted,  —  are  due  to 
such  alternations  in  the  character  of  the  rocks. 

In  consequence  of  the  influence  of  time, 
weather,  atmospheric  action  of  all  kinds,  the 
apparent  relation  of  beds  has  often  become  so 
completely  reversed  that  it  is  exceedingly  diffi- 
cult to  trace  their  original  relation.  Take,  for 
instance,  the  following  case.  An  eruption  has 
upheaved  the  strata  over  a  given  surface  in  such 
a  manner  as  to  lift  them  into  a  mountain,  crack- 
ing open  the  upper  beds,  but  leaving  the  lower 
ones  unbroken.  We  have  then  a  valley  on  a 
mountain-summit  between  two  crests  resembling 
the  one  already  shown  in  Figure  4.  Such  a  nar- 
row passage  between  two  crests  may  be  changed 
in  the  course  of  time  to  a  wide  expansive  valley 
by  the  action  of  the  rains,  frosts,  and  other  disin- 
tegrating agents,  and  the  relative  position  of  the 
strata  forming  its  walls  may  seem  to  be  entirely 
changed. 


MOUNTAINS  AND  THEIR  ORIGIN.  109 

Suppose,  for  example,  that  the  two  upper  lay- 
ers of  the  strata  rent  apart  by  the  upheaval  of 
the  mountain  are  limestone  and  sandstone,  while 

the  third  is  clay  and  the 
fourth  again  limestone 
(as  in  Figure  6).  Clay 
is  soft,  and  yields  very 
readily  to  the  action  of 
rain.  In  such  a  valley 
the  edges  of  the  strata  forming  its  walls  are  of 
course  exposed,  and  the  clay  formation  will  be 
the  first  to  give  way  under  the  action  of  external 
influences.  Gradually  the  rains  wear  away  its 
substance  till  it  is  completely  hollowed  out.  By 
the  disintegration  of  the  bed  beneath  them,  the 
lime  and  sandstone  layers  above  lose  their  sup- 
port and  crumble  down,  and  this  process  goes  on, 
the  clay  constantly  wearing  away,  and  the  lime 
and  sand  above  consequently  falling  in,  till  the 
upper  beds  have  receded  to  a  great  distance,  the 
valley  has  opened  to  a  wide  expanse  instead  of 
being  enclosed  between  two  walls,  and  the  lowest 
limestone  bed  now  occupies 
the  highest  position  on  the 
mountain.  Figure  7  repre- 
sents one  of  the  crests  shown 
Fis- ?•  in  Figure  6,  after  such  a  level- 

ling process  has  changed  its  outline. 

But  the  phenomena  of  eruptions  in  mountain- 


110  MOUNTAINS  AND  THEIR  ORIGIN. 

chains  are  far  more  difficult  to  trace  than  the 
effects  thus  gradually  produced.  Plutonic  action 
has,  indeed,  played  the  most  fantastic  tricks  with 
the  crust  of  the  earth,  which  seems  as  plastic  in 
the  grasp  of  the  fiery  power  hidden  within  it  as 
does  clay  in  the  hands  of  the  sculptor. 

We  have  seen  that  an  equal  vertical  pressure 
from  below  produces  a  regular  dome,  —  or  that, 
if  the  dome  be  broken  through,  a  granite  crest  is 
formed,  with  stratified  materials  resting  against 
its  slopes.  But  the  pressure  has  often  been 
oblique  instead  of  vertical,  and  then  the  slope  of 
the  mountain  is  uneven,  with  a  gradual  ascent 
on  one  side  and  an  abrupt  wall  on  the  other ;  or 
in  some  instances  the  pressure  has  been  so  lateral 
that  the  mountain  is  overturned  and  lies  upon  its 
side,  and  there  are  still  other  cases  where  one 
mountain  has  been  tilted  over  and  has  fallen 
upon  an  adjoining  one. 

Sometimes,  when  beds  have  been  torn  asunder, 
one  side  of  them  has  been  forced  up  above  the 
other;  and  there  are  even  instances  where  one 
side  of  a  mountain  has  been  forced  under  the 
surface  of  the  earth,  while  the  other  has  re- 
mained above.  Stratified  beds  of  rock  are  occa- 
sionally found  which  have  been  so  completely 
capsized,  that  the  layers,  which  were  of  course 
deposited  horizontally,  now  stand  on  end,  side  by 
side,  in  vertical  rows.  I  remember,  after  a  lee- 


MOUNTAINS  AND  THEIR   ORIGIN.  Ill 

tare  on  some  of  these  extravagances  in  moun- 
tain-formations, a  friend  said  to  me,  not  inaptly, 
— "  One  can  hardly  help  thinking  of  these  ex- 
traordinary contortions  as  a  succession  of  frantic 
frolics :  the  mountains  seem  like  a  troop  of  rol- 
licking boys,  hunting  one  another  in  and  out  and 
up  and  down  in  a  gigantic  game  of  hide-and- 
seek." 

The  width  of  the  arch  of  a  mountain  depends 
in  a  great  degree  on  the  thickness  and  flexibility 
of  the  beds  of  which  it  is  composed.  There  is 
not  only  a  great  difference  in  the  consistency  of 
stratified  material,  but  every  variety  in  the  thick- 
ness of  the  layers,  from  an  inch,  and  even  less, 
to  those  measuring  from  ten  or  twenty  to  one 
hundred  feet  and  more  in  depth,  without  marked 
separation  of  the  successive  beds.  This  is  ac- 
counted for  by  the  frequent  alternations  of  sub- 
sidence and  upheaval ;  the  continents  having 
tilted  sometimes  in  one  direction,  sometimes  in 
another,  so  that  in  certain  localities  there  has 
been  much  water  and  large  deposits,  while  else- 
where the  water  was  shallow  and  the  deposits 
consequently  less.  Thin  and  flexible  strata  have 
been  readily  lifted  into  a  sharp,  abrupt  arch  with 
narrow  base,  while  the  thick  and  rigid  beds  have 
been  forced  up  more  slowly  in  a  wider  arch  with 
broader  base. 

Table-lands  are  only  long  unbroken  folds  of 


112  MOUNTAINS  AND  THEIR   ORIGIN. 

the  earth's  surface,  raised  uniformly  and  in  one 
direction.  It  is  the  same  pressure  from  below, 
which,  when  acting  with  more  intense  force  in 
one  direction,  makes  a  narrow  and  more  abrupt 
fold,  forming  a  mountain-ridge,  but,  when  acting 
over  a  wider  surface  with  equal  force,  produces 
an  extensive  uniform  elevation.  If  the  pressure 
be  strong  enough,  it  will  cause  cracks  and  dislo- 
cations at  the  edges  of  such  a  gigantic  fold,  and 
then  we  have  table-lands  between  two  mountain- 
chains,  like  the  Gobi  in  Asia  between  the  Altai 
Mountains  and  the  Himalayas,  or  the  table-land 
enclosed  between  the  Rocky  Mountains  and  the 
coast-range  of  the  Pacific  shore. 

We  do  not  think  of  table-lands  as  mountainous 
elevations,  because  their  broad,  flat  surfaces  re- 
mind us  of  the  level  tracts  of  the  earth;  but 
some  of  the  table-lands  are  nevertheless  higher 
than  many  mountain-chains,  as,  for  instance,  the 
Gobi,  which  is  higher  than  the  Alleghanies,  or 
the  Jura,  or  the  Scandinavian  Alps.  One  of 
Humboldt's  masterly  generalizations  was  his  esti- 
mate of  the  average  thickness  of  the  different 
continents,  supposing  their  heights  to  be  levelled 
and  their  depressions  filled  up,  and  he  found  that 
upon  such  an  estimate  Asia  would  be  much 
higher  than  America,  notwithstanding  the  great 
mountain-chains  of  the  latter.  The  extensive 
table-land  of  Asia,  with  the  mountains  adjoining 


MOUNTAINS  AND  THEIR   ORIGIN.  113 

it,  outweighed  the  Alleghanies,  the  Kocky  Moun- 
tains, the  Coast-Chain,  and  the  Andes. 

When  we  compare  the  present  state  of  our 
knowledge  of  geological  phenomena  with  that 
which  prevailed  fifty  years  ago,  it  seems  difficult 
to  believe  that  so  great  and  important  a  change 
can  have  been  brought  about  in  so  short  a  time. 
It  was  on  German  soil  and  by  German  students 
that  the  foundation  was  laid  for  the  modern  sci- 
ence of  systematic  geology. 

In  the  latter  part  of  the  eighteenth  century, 
extensive  mining  operations  in  Saxony  gave  rise 
to  an  elaborate  investigation  of  the  soil  for  prac- 
tical purposes.  It  was  found  that  the  rocks  con- 
sisted of  a  succession  of  materials  following  each 
other  in  regular  sequence,  some  of  which  were 
utterly  worthless  for  industrial  purposes,  while 
others  were  exceedingly  valuable.  The  Muschel- 
Kalk  formation,  so  called  from  its  innumerable 
remains  of  shells,  and  a  number  of  strata  under- 
lying it,  must  be  penetrated  before  the  miners 
reached  the  rich  veins  of  Kupferschiefer  (copper 
slate),  and  below  this  came  what  was  termed  the 
Todtliegende  (dead  weight),  so  called  because  it 
contained  no  serviceable  materials  for  the  useful 
arts,  and  had  to  be  removed  before  the  valuable 
beds  of  coal  lying  beneath  it,  and  making  the 
base  of  the  series,  could  be  reached.  But  while 


114  MOUNTAINS  AND  THEIR  ORIGIN. 

the  workmen  wrought  at  these  successive  layers 
of  rock  to  see  what  they  would  yield  for  practical 
purposes,  a  man  was  watching  their  operations 
who  considered  the  crust  of  the  earth  from  quite 
another  point  of  view. 

Abraham  Gottlob  Werner  was  born  more  than 
a  century  ago  in  Upper  Lusatia.  His  very  in- 
fancy seemed  to  shadow  forth  his  future  studies, 
for  his  playthings  were  the  minerals  he  found  in 
his  father's  forge.  At  a  suitable  age  he  was 
placed  at  the  mining  school  of  Freiberg  in  Sax- 
ony, and  having,  when  only  twenty-four  years  of 
age,  attracted  attention  in  the  scientific  world  by 
the  publication  of  an  "  Essay  on  the  Characters 
of  Minerals,"  he  was  soon  after  appointed  to  the 
professorship  of  mineralogy  in  Freiberg.  His  lot 
in  life  could  not  have  fallen  in  a  spot  more  ad- 
vantageous for  his  special  studies,  and  the  enthu- 
siasm with  which  he  taught  communicated  itself 
to  his  pupils,  many  of  whom  became  his  devoted 
disciples,  disseminating  his  views  in  their  turn 
with  a  zeal  which  rivalled  the  master's  ardor. 

Werner  took  advantage  of  the  mining  opera- 
tions going  on  in  his  neighborhood,  the  blasting, 
sinking  of  shafts,  etc.,  to  examine  critically  the 
composition  of  the  rocks  thus  laid  open,  and  the 
result  of  his  analysis  was  the  establishment  of  the 
Neptunic  school  of  geology  alluded  to  in  a  pre- 
vious article,  and  so  influential  in  science  at  the 


MOUNTAINS  AND   THEIR   OEIGIN.  115 

close  of  the  eighteenth  and  the  opening  of  the 
nineteenth  century.  From  the  general  character 
of  these  rocks,  as  well  as  the  number  of  marine 
shells  contained  in  them,  he  convinced  himself 
that  the  whole  series,  including  the  Coal,  the 
Todtliegende,  the  Kupferschiefer,  the  Zechstein,  the 
Red  Sandstone,  and  the  Muschel-Kalk,  had  been 
deposited  under  the  agency  of  water,  and  were 
the  work  of  the  ocean. 

Thus  far  he  was  right,  with  the  exception  that 
he  did  not  include  the  accumulation  of  materials 
by  the  local  action  of  fresh  water  afterwards 
traced  by  Cuvier  and  Brogniart  in  the  Tertiary 
deposits  about  Paris.  But  from  these  data  he 
went  a  step  too  far,  and  assumed  that  all  rocks, 
except  the  modern  lavas,  must  have  been  accu- 
mulated by  the  sea,  —  believing  even  the  gran- 
ites, porphyries,  and  basalts  to  have  been  depos- 
ited in  the  ocean  and  crystallized  from  the  sub- 
stances it  contained  in  solution. 

But,  in  the  mean  time,  James  Hutton,  a  Scotch 
geologist,  was  looking  at  phenomena  of  a  like 
character  from  a  very  different  point  of  view. 
In  the  neighborhood  of  Edinburgh,  where  he 
lived,  was  an  extensive  region  of  trap-rock, — 
that  is,  of  igneous  rock,  which  had  forced  itself 
through  the  stratified  deposits,  sometimes  spread- 
ing in  a  continuous  sheet  over  large  tracts,  or 
splitting  them  open  and  filling  all  the  interstices 


116  MOUNTAINS  AND  THEIR  ORIGIN. 

and  cracks  so  formed.  Thus  he  saw  igneous 
rocks  not  only  covering  or  underlying  stratified 
deposits,  but  penetrating  deep  into  their  struc- 
ture, forming  dikes  at  right  angles  with  them, 
and  presenting,  in  short,  all  the  phenomena  be- 
longing to  volcanic  rocks  in  contact  with  strati- 
fied materials.  He  again  pushed  his  theory  too 
far,  and,  inferring  from  the  phenomena  immedi- 
ately about  him  that  heat  had  been  the  chief 
agent  in  the  formation  of  the  earth's  crust,  he 
was  inclined  to  believe  that  the  stratified  mate- 
rials also  were  in  part  at  least  due  to  this  cause. 
I  have  alluded  in  a  former  number  to  the  hot  dis- 
putes and  long-contested  battles  of  geologists 
upon  this  point.  It  was  a  pupil  of  Werner's  who 
at  last  set  at  rest  this  much  vexed  question. 

At  the  age  of  sixteen,  in  the  year  1790,  Leo- 
pold von  Buch  was  placed  under  Werner's  care 
at  the  mining  school  of  Freiberg.  Werner  found 
him  a  pupil  after  his  own  heart.  Warmly  adopt- 
ing his  teacher's  theory,  he  pursued  his  geologi- 
cal studies  with  the  greatest  ardor,  and  continued 
for  some  time  under  the  immediate  influence  and 
guidance  of  the  Freiberg  professor.  His  univer- 
sity studies  over,  however,  he  began  to  pursue  his 
investigations  independently,  and  his  geological 
excursions  led  him  into  Italy,  where  his  confi- 
dence in  the  truth  of  Werner's  theory  began  to 
be  shaken.  A  subsequent  visit  to  the  region  of 


MOUNTAINS  AND   THEIR   ORIGIN.  117 

extinct  volcanoes  in  Auvergne,  in  the  South  of 
France,  convinced  him  that  the  aqueous  theory 
was  at  least  partially  wrong,  and  that  fire  had 
been  an  active  agent  in  the  rock-formations  of 
past  times.  This  result  did  not  change  the  con- 
victions of  his  master,  Werner,  who  was  too  old 
or  too  prejudiced  to  accept  the  later  views,  which 
were  nevertheless  the  result  of  the  stimulus  he 
himself  had  given  to  geological  investigations. 

But  Yon  Buch  was  indefatigable.  For  years 
he  lived  the  life  of  an  itinerant  geologist.  With 
a  shirt  and  a  pair  of  stockings  in  his  pocket,  and 
a  geological  hammer  in  his  hand,  he  travelled  all 
over  Europe  on  foot.  The  results  of  his  foo1>- 
journey  to  Scandinavia  were  among  his  most  im- 
portant contributions  to  geology.  He  went  also 
to  the  Canary  Islands ;  and  it  is  in  his  extensive 
work  on  the  geological  formations  of  these  islands 
that  he  showed  conclusively  not  only  the  Plutonic 
character  of  all  unstratified  rocks,  but  also  that 
to  their  action  upon  the  stratified  deposits  the  in- 
equalities of  the  earth's  surface  are  chiefly  due. 
He  first  demonstrated  that  the  melted  masses 
within  the  earth  had  upheaved  the  materials  de- 
posited in  layers  upon  its  surface,  and  had  thus 
formed  the  mountains. 

No  geologist  has  ever  collected  a  larger  amount 
of  facts  than  Yon  Buch,  and  to  him  we  owe  a 
great  reform  not  only  in  geological  Drinciples, 


118  MOUNTAINS  AND  THEIR   ORIGIN. 

but  in  methods  of  study  also.  An  amusing  anec- 
dote is  told  of  him,  as  illustrating  his  untiring 
devotion  to  his  scientific  pursuits.  In  studying 
the  rocks,  he  had  become  engaged  also  in  the  in- 
vestigation of  the  fossils  contained  in  them.  He 
was  at  one  time  especially  interested  in  the  Tere- 
bratulce,  certain  fossil  shells  found  in  great  abun- 
dance in  all  stratified  rocks,  and  one  evening  in 
Berlin,  where  he  was  engaged  in  the  study  of 
these  remains,  he  came  across  a  notice  in  a  Swed- 
ish work  of  a  particular  species  of  that  family 
which  he  could  not  readily  identify  without  see- 
ing the  original  specimens.  The  next  morning 
Von  Buch  was  missing,  and  as  he  had  invited 
guests  to  dine  with  him,  some  anxiety  was  felt  on 
account  of  his  non-appearance.  On  inquiry,  it 
was  found  that  he  was  already  far  on  his  way  to 
Sweden :  he  had  started  by  daylight  on  a  pilgrim- 
age after  the  new,  or  rather  the  old,  Terebratula. 
I  tell  the  story  as  I  heard  it  from  one  of  the  dis- 
appointed guests. 

All  great  natural  phenomena  impressed  him 
deeply.  On  one  occasion  it  was  my  good  fortune 
to  make  one  of  a  party  from  the  "  Helvetic  Asso- 
ciation for  the  Advancement  of  Science "  on  an 
excursion  to  the  eastern  extremity  of  the  Lake  of 
Geneva.  I  well  remember  the  expressive  gesture 
of  Von  Buch,  as  he  faced  the  deep  gorge  through 
which  the  Rhone  issues  from  the  interior  of  the 


MOUNTAINS  AND   THEIR   ORIGIN.  119 

Alps.  While  others  were  chatting  and  laughing 
about  him,  he  stood  for  a  moment  absorbed  in 
silent  contemplation  of  the  grandeur  of  the  scene, 
then  lifted  his  hat  and  bowed  reverently  before 
the  mountains. 

Next  to  Yon  Buch,  no  man  has  done  more  for 
modern  geology  than  Elie  de  Beaumont,  the  great 
French  geologist.  Perhaps  the  most  important 
of  his  generalizations  is  that  by  which  he  has 
given  us  the  clew  to  the  limitation  of  the  differ- 
ent epochs  in  past  times  by  connecting  them  with 
the  great  revolutions  in  the  world's  history.  He 
has  shown  us  that  the  great  changes  in  the  aspect 
of  the  globe,  as  well  as  in  its  successive  sets  of 
animals,  coincide  with  the  mountain-upheavals. 

I  might  add  a  long  list  of  names,  American  as 
well  as  European,  which  will  be  forever  honored 
in  the  history  of  science  for  their  contributions 
to  geology  in  the  last  half-century.  But  I  have 
intended  only  to  close  this  chapter  on  mountains 
with  a  few  words  respecting  the  men  who  first  in- 
vestigated their  intimate  structural  organization, 
and  established  methods  of  study  in  reference  to 
them  now  generally  adopted  throughout  the  sci- 
entific world.  In  my  next  article  I  shall  proceed 
to  give  some  account  of  special  geological  forma- 
tions in  Europe,  and  the  gradual  growth  of  that 
continent. 


V. 
THE    GROWTH    OF    CONTINENTS. 

BEFORE  entering  upon  a  sketch  of  the  growth 
of  the  European  Continent  from  'the  earliest 
times  until  it  reached  its  present  dimensions  and 
outlines,  I  will  say  something  of  the  growth  of 
continents  in  general,  connecting  these  remarks 
with  a  few  words  of  explanation  respecting  some 
geological  terms,  which,  although  in  constant  use, 
are  nevertheless  not  clearly  defined.  I  will  ex- 
plain, at  the  outset,  the  meaning  I  attach  to  them 
and  the  sense  in  which  I  use  them,  that  there 
may  be  no  misunderstanding  between  me  and  my 
readers  on  this  point.  The  words  Age,  Epoch, 
Period,  Formation,  may  be  found  on  almost  every 
page  of  any  modern  work  on  geology ;  but  if  we 
sift  the  matter  carefully,  we  shall  find  that  there 
is  a  great  uncertainty  as  to  the  significance  of 
these  terms,  and  that  scarcely  any  two  geologists 
use  them  in  the  same  sense.  Indeed,  I  shall  not 
be  held  blameless  in  this  respect  myself;  for,  on 
looking  over  preceding  articles,  I  find  that  I  have, 
from  old  habit,  used  somewhat  indiscriminately 


THE  GROWTH  OF  CONTINENTS.      121 

names  which  should  have  a  perfectly  definite  and 
invariable  meaning.  As  long  as  zoological  no- 
menclature was  uncontrolled  by  any  principle, 
the  same  vagueness  and  indecision  prevailed  here 
also.  The  words  Genus,  Order,  Class,  as  well  as 
those  applied  to  the  most  comprehensive  division 
of  all  in  the  animal  kingdom,  the  primary 
branches  or  types,  were  used  indiscriminately, 
and  often  allowed  to  include  under  one  name 
animals  differing  essentially  in  their  structural 
character.  It  is  only  since  it  has  been  found 
that  all  these  groups  are  susceptible  of  limitation, 
according  to  distinct  categories  of  structure,  that 
our  nomenclature  has  assumed  a  more  precise 
and  definite  significance.  Even  now  there  is  still 
some  inconsistency  among  zoologists  as  to  the  use 
of  special  terms,  arising  from  their  individual  dif- 
ferences in  appreciating  structural  features ;  but 
I  believe  it  to  be,  nevertheless,  true,  that  genera, 
orders,  classes,  etc.,  are  not  merely  larger  or 
smaller  groups  of  the  same  kind,  but  are  really 
based  upon  distinct  categories  of  structure.  As 
soon  as  such  a  principle  is  admitted  in  geology, 
and  investigators  recognize  certain  physical  and 
organic  conditions,  more  or  less  general  in  their 
action,  as  characteristic  of  all  those  chapters  in 
geological  history  designated  as  Ages,  Epochs, 
Periods,  Formations,  etc.,  all  vagueness  will  van- 
ish from  the  scientific  nomenclature  of  this  de- 

6 


122       THE  GROWTH  OF  CONTINENTS. 

partment  also,  and  there  will  be  no  hesitation  as 
to  the  use  of  words  for  which  we  shall  then  have 
a  positive,  definite  meaning. 

Although  the  fivefold  division  of  Werner,  by 
which  he  separated  the  rocks  into  Primitive, 
Transition,  Secondary,  Alluvial,  and  Volcanic, 
proved  to  be  based  on  a  partial  misapprehension 
of  the  nature  of  the  earth-crust,  yet  it  led  to 
their  subsequent  division  into  the  three  great 
groups  now  known  as  the  Primary,  or  Palaeozoic, 
as  they  are  sometimes  called,  because  here  are 
found  the  first  organic  remains,  the  Secondary, 
and  the  Tertiary.  I  have  said  in  a  previous  arti- 
cle that  the  general  unity  of  character  prevailing 
throughout  these  three  divisions,  so  that,  taken 
from  the  broadest  point  of  view,  each  one  seems 
a  unit  in  time,  justifies  the  application  to  them 
of  that  term,  Age,  by  which  we  distinguish  in 
human  history  those  periods  marked  throughout 
by  one  prevailing  tendency ;  —  as  we  say  the  age 
of  Egyptian  or  Greek  or  Roman  civilization, — 
the  age  of  stone  or  iron  or  bronze.  I  believe  that 
this  division  of  geological  history  into  these  great 
sections  or  chapters  is  founded  upon  a  recogni- 
tion of  the  general  features  by  which  they  are 
characterized. 

Passing  over  the  time  when  the  first  stratified 
deposits  were  accumulated  under  a  universal 
ocean  in  which  neither  animals  nor  plants  ex- 


THE  GROWTH  OF  CONTINENTS.       123 

isted,  there  was  an  age  in  the  physical  history  of 
the  world  when  the  lands  consisted  of  low  islands, 
—  when  neither  great  depths  nor  lofty  heights 
diversified  the  surface  of  the  earth,  —  when  both 
the  animal  and  vegetable  creation,  however  nu- 
merous, was  inferior  to  the  later  ones,  and  com- 
paratively uniform  in  character,  —  when  marine 
Cryptogams  were  the  highest  plants,  and  Fishes 
were  the  highest  'animals.  And  this  broad  state- 
ment holds  good  for  the  whole  of  that  time,  even 
though  it  was  not  without  its  minor  changes,  its 
new  forms  of  animal  and  vegetable  life,  its  varia- 
tions of  level,  its  upheavals  and  subsidences  ;  for, 
nevertheless,  through  its  whole  duration,  it  was 
the  age  of  low  detached  lands,  —  it  was  the  age 
of  Cryptogams,  —  it  was  the  age  of  Fishes.  From 
its  beginning  to  its  close,  no  higher  type  in  the 
animal  kingdom,  no  loftier  group  in  the  vegetable 
world,  made  its  appearance. 

There  was  an  age  in  the  physical  history  of  the 
world  when  the  patches  of  land  already  raised 
above  the  water  became  so  united  as  to  form  large 
islands ;  and  though  the  aspect  of  the  earth  re- 
tained its  insular  character,  yet  the  size  of  the 
islands,  their  tendency  to  coalesce  by  the  addition 
of  constantly  increasing  deposits,  and  thus  to 
spread  into  wider  expanses  of  dry  land,  marked 
the  advance  toward  the  formation  of  continents. 
This  extension  of  the  dry  land  was  brought  about 


124       THE  GROWTH  OF  CONTINENTS. 

not  only  by  the  gradual  accumulation  of  mate- 
rials, but  also  by  the  upheaval  of  large  tracts  of 
stratified  deposits  ;  for,  though  the  loftiest  moun- 
tain-chains did  not  yet  exist,  ranges  like  those 
of  the  Alleghanies  and  the  Jura  belong  to  this 
division  of  the  world's  history.  During  this  time, 
the  general  character  of  the  animal  and  vegetable 
kingdoms  was  higher  than  during  the  previous 
age.  Reptiles,  many  and  various,  gigantic  in 
size,  curious  in  form,  some  of  them  recalling  the 
structure  of  fishes,  others  anticipating  birdlike 
features,  gave  a  new  character  to  the  animal 
world,  while  in  the  vegetable  world  the  reign  of 
the  aquatic  Cryptogams  was  over,  and  terrestrial 
Cryptogams,  and,  later,  Gymnosperms  and  Mono- 
cotyledonous  trees,  clothed  the  earth  with  foliage. 
Such  was  the  character  of  this  second  age,  from 
its  opening  to  its  close ;  and  though  there  are 
indications  that,  before  it  was  wholly  past,  some 
low,  inferior  Mammalian  types  of  the  Marsupial 
kind  were  introduced,*  and  also  a  few  Dicotyle- 
donous plants,  yet  they  were  not  oiumerous  or 

*  I  say  nothing  of  the  traces  of  Birds  in  the  Secondary  de- 
posits, because  the  so-called  bird-tracks  seem  to  me  of  very 
doubtful  character ;  and  it  is  also  my  opinion  that  the  remains 
of  a  feathered  animal  recently  found  in  the  Solenhofen  litho- 
graphic limestone,  and  believed  to  be  a  bird  by  some  naturalists, 
do  not  belong  to  a  genuine  bird,  but  to  one  of  those  synthetic 
types  before  alluded  to,  in  which  reptilian  structure  is  combined 
with  certain  birdlike  features. 


THE  GEOWTH  OF  CONTINENTS.       125 

striking  enough  to  change  the  general  aspect  of 
the  organic  world.  This  age  was  throughout,  in 
its  physical  formation,  the  age  of  large  continen- 
tal islands  ;  while  in  its  organic  character  it  was 
the  age  of  Reptiles  as  the  highest  animal  type, 
and  of  Gymnosperms  and  Monocotyledonous 
plants  as  the  highest  vegetable  groups. 

There  was  an  age  in  the  physical  history  of  the 
world  when  great  ranges  of  mountains  bound  to- 
gether in  everlasting  chains  the  islands  which 
had  already  grown  to  continental  dimensions, — 
when  wide  tracts  of  land,  hitherto  insular  in 
character,  became  soldered  into  one  by  the  up- 
heaval of  Plutonic  masses  which  stretched  across 
them  all  and  riveted  them  forever  with  bolts  of 
granite,  of  porphyry,  and  of  basalt.  Thus  did 
the  Rocky  Mountains  and  the  Andes  bind  to- 
gether North  and  South  America ;  the  Pyrenees 
united  Spain  to  France  ;  the  Alps,  the  Caucasus, 
and  the  Himalayas  bound  Europe  to  Asia.  The 
class  of  Mammalia  was  now  at  the  head  of  the 
animal  kingdom ;  huge  quadrupeds  possessed  the 
earth,  and  dwelt  in  forests  characterized  by  plants 
of  a  higher  order  than  any  preceding  ones,  —  the 
Beeches,  Birches,  Maples,  Oaks,  and  Poplars  of 
the  Tertiaries.  But  though  the  continents  had 
assumed  their  permanent  outlines,  extensive 
tracts  of  land  still  remained  covered  with  ocean. 
Inland  seas,  sheets  of  water  like  the  Mediterra- 


126       THE  GROWTH  OF  CONTINENTS. 

nean,  so  unique  in  our  world,  were  then  numer- 
ous. Physically  speaking,  this  was  the  age  of 
continents  broken  by  large  inland  seas ;  while  in 
the  organic  world  it  was  the  age  of  Mammalia 
among  animals,  and  of  extensive  Dicotyledonous 
forests  among  plants.  In  a  certain  sense  it  was 
the  age  of  completion,  —  the  one  which  ushered 
in  the  crowning  work  of  creation. 

There  was  an  age  in  the  physical  history  of  the 
world  (it  is  in  its  infancy  still)  when  Man,  with 
the  animals  and  plants  that  were  to  accompany 
him,  was  introduced  upon  the  globe,  which  had 
acquired  all  its  modern  characters.  At  last  the 
continents  were  redeemed  from  the  water,  and 
all  the  earth  was  given  to  this  new  being  for  his 
home.  Among  all  the  types  born  into  the  ani- 
mal kingdom  before,  there  had  never  been  one  to 
which  positive  limits  had  not  been  set  by  a  law 
of  geographical  distribution  absolutely  impassible 
to  all.  For  Man  alone  those  boundaries  were 
removed.  He,  with  the  domestic  animals  and 
plants  which  were  to  be  the  companions  of  all  his 
pilgrimages,  could  wander  over  the  whole  earth 
and  choose  his  home.  Placed  at  the  head  of  cre- 
ation, gifted  with  intellect  to  make  both  animals 
and  plants  subservient  to  his  destinies,  his  intro- 
duction upon  the  earth  marks  the  last  great  divis- 
ion in  the  history  of  our  planet.  To  designate 
these  great  divisions  in  time,  I  would  urge,  for 


THE  GROWTH  OF  CONTINENTS.       127 

the  reasons  above  stated,  that  the  term  which  is 
indeed  often,  though  not  invariably,  applied  to 
them,  be  exclusively  adopted,  —  that  of  the  Ages 
of  Nature. 

But  these  Ages  are  themselves  susceptible  of 
subdivisions,  which  should  also  be  accurately  de- 
nned. What  is  the  nature  of  these  subdivisions  ? 
They  are  all  connected  with  sudden  physical 
changes  in  the  earth's  surface,  more  or  less  lim- 
ited in  their  action,  these  changes  being  them- 
selves related  to  important  alterations  in  the 
organic  world.  Although  I  have  stated  that  one 
general  character  prevailed  during  each  of  the 
Ages,  yet  there  was  nevertheless  a  constant  pro- 
gressive action  running  through  them  all,  and  at 
various  intervals  both  the  organic  and  the  physi- 
cal world  received  a  sudden  impulse  in  conse- 
quence of  marked  and  violent  changes  in  the 
earth-crust,  bringing  up  new  elevations,  while  at 
the  same  time  the  existing  animal  creation  was 
brought  to  a  close,  and  a  new  set  of  beings  was 
introduced.  These  changes  are  not  yet  accu- 
rately defined  in  America,  because  the  age  of  her 
mountains  is  not  known  with  sufficient  exactness ; 
but  their  limits  have  been  very  extensively  traced 
-in  Europe,  and  this  coincidence  of  the  various 
upheavals  with  the  introduction  of  a  new  popu- 
lation differing  entirely  from  the  preceding  one, 
has  been  demonstrated  so  clearly,  that  it  may  be 


128       THE  GEOWTH  OF  CONTINENTS. 

considered  as  an  ascertained  law.  What  name, 
then,  is  most  appropriate  for  the  divisions  thus 
marked  by  sudden  and  violent  changes?  It 
seems  to  me,  from  their  generally  accepted  mean- 
ing, that  the  word  Epoch  or  Era,  both  of  which 
have  been  widely,  though  indiscriminately,  used 
in  geology,  is  especially  applicable  here.  In  their 
common  use,  they  imply  a  condition  of  things 
determined  by  some  decisive  event.  In  speaking 
of  human  affairs,  we  say,  "  It  was  an  epoch  or  an 
era  in  history,"  —  or  in  a  more  limited  sense, 
"  It  was  an  epoch  in  the  life  of  such  or  such  a 
man."  It  at  once  conveys  the  idea  of  an  impor- 
tant change  connected  with  or  brought  about  by 
some  striking  occurrence.  Such  were  those  di- 
visions in  the  history  of  the  earth  when  a  violent 
convulsion  in  the  surface  of  the  globe  and  a 
change  in  its  inhabitants  ushered  in  a  new  aspect 
of  things. 

I  have  said  that  we  owe  to  Elie  de  Beaumont 
the  discovery  of  this  connection  between  the  suc- 
cessive upheavals  and  the  different  sets  of  ani- 
mals and  plants  which  have  followed  each  other 
on  the  globe.  We  have  seen,  in  the  preceding 
article  upon  the  formation  of  mountains,  that  the 
dislocations  thus  produced  show  the  interruptions 
between  successive  deposits:  as,  for  instance, 
where  certain  strata  are  raised  upon  the  sides  of 
a  mountain,  while  other  strata  rest  unconformably , 


THE  GEOWTH  OF  CONTINENTS.       129 

as  it  is  called,  above  them  at  its  base,  —  this  term, 
unconformable,  signifying  merely  that  the  two 
sets  of  strata  are  placed  at  an  entirely  different 
angle,  and  must  therefore  belong  to  two  distinct 
sets  of  deposits.  But  there  are  two  series  of 
geological  facts  connected  with  this  result  which 
are  often  confounded,  though  they  arise  from 
very  different  causes.  One  is  that  described 
above,  in  which,  a  certain  series  of  beds  having 
been  raised  out  of  their  natural  horizontal  posi- 
tion, another  series  has  been  deposited  upon 
them,  thus  resting  unconformably  above.  The 
other  is  where,  one  set  of  beds  having  been  de- 
posited over  any  given  region,  at  a  later  time,  in 
consequence  of  a  recession  of  the  sea-shore,  for 
instance,  or  of  some  other  gradual  disturbance 
of  the  surface,  the  next  set  of  beds  accumulated 
above  them  cover  a  somewhat  different  area,  and 
are  therefore  not  conformable  with  the  first, 
though  parallel  with  them.  This  difference, 
however  slight,  is  sufficient  to  show  that  some 
shifting  of  the  ground  on  which  they  were  accu- 
mulated must  have  taken  place  between  the  two 
series  of  deposits. 

This  distinction  must  not  be  confounded  with 
that  made  by  Elie  de  Beaumont :  we  owe  it  to 
D'Orbigny,  who  first  pointed  out  the  importance 
of  distinguishing  the  dislocations  produced  by 
gradual  movements  of  the  earth  from  those 

6*  I 


130       THE  GEOWTH  OF  CONTINENTS. 

caused  by  mountain-upheavals.  The  former  are 
much  more  numerous  than  the  latter,  and  in 
every  epoch  geologists  have  distinguished  a  num- 
ber of  such  changes  in  the  surface  of  the  earth, 
accompanied  by  the  introduction  of  a  new  set  of 
animals,  though  the  changes  in  the  organic  world 
are  not  so  striking  as  those  which  coincide  with 
the  mountain-upheavals.  Still,  to  the  eye  of  the 
geologist  they  are  quite  as  distinct,  though  less 
evident  to  the  ordinary  observer.  To  these  divis- 
ions it  seems  to  me  that  the  name  of  Period  is 
rightly  applied,  because  they  seem  to  have  been 
brought  about  by  the  steady  action  of  time,  and 
by  gradual  changes,  rather  than  by  any  sudden 
or  violent  convulsion. 

It  was  my  good  fortune  to  be  in  some  degree 
connected  with  the  investigations  respecting  the 
limitation  of  Periods,  for  which  the  geology  of 
Switzerland  afforded  peculiar  facilities.  My  early 
home  was  near  the  foot  of  the  Jura,  where  I  con- 
stantly faced  its  rounded  domes  and  the  slope  by 
which  they  gently  descend  to  the  plain  of  Swit- 
zerland. I  have  heard  it  said  that  there  is  some- 
thing monotonous  in  the  continuous  undulations 
of  this  range,  so  different  from  the  opposite  one 
of  the  Alps.  But  I  think  it  is  only  by  contrast 
that  it  seems  wanting  in  vigor  and  picturesque- 
ness  ;  and  those  who  live  in  its  neighborhood  be- 
come very  much  attached  to  the  more  peaceful 


THE  GKOWTH  OF  CONTINENTS.       131 

character  of  its  scenery.  Perhaps  my  readers 
will  pardon  the  digression,  if  I  interrupt  our  geo- 
logical discussion  for  a  moment,  to  offer  them  a 
word  of  advice,  though  it  be  uncalled  for.  I 
have  often  been  asked  by  friends  who  were  in- 
tending to  go  to  Europe,  what  is  the  most  favor- 
able time  in  the  day  and  the  best  road  to  enter 
Switzerland  in  order  to  have  at  once  the  finest 
impression  of  the  mountains.  My  answer  is  al- 
ways, —  Enter  it  in  the  afternoon  over  the  Jura. 
If  you  are  fortunate,  and  have  one  of  the  bright, 
soft  afternoons  that  sometimes  show  the  Alps  in 
their  full  beauty,  as  you  descend  the  slope  of  the 
Jura,  from  which  you  command  the  whole  pano- 
rama of  the  opposite  range,  you  may  see,  as  the 
day  dies,  the  last  shadow  pass  with  strange  rapid- 
ity from  peak  to  peak  of  the  Alpine  summits. 
The  passage  is  so  rapid,  so  sudden,  as  the  shadow 
vanishes  from  one  height  and  appears  on  the 
next,  that  it  seems  like  the  step  of  some  living 
spirit  of  the  mountains.  Then,  as  the  sun  sinks, 
it  sheds  a  brilliant  glow  across  them,  and  upon 
that  follows,  —  strangest  effect  of  all,  —  a  sudden 
pallor,  an  ashy  paleness  on  the  mountains,  that 
has  a  ghastly,  chilly  look.  But  this  is  not  their 
last  aspect:  after  the  sun  has  vanished  out  of 
sight,  in  place  of  the  glory  of  his  departure,  and 
of  the  corpse-like  pallor  which  succeeded  it,  there 
spreads  over  the  mountains  a  faint  blush  that  dies 


132       THE  GROWTH  OF  CONTINENTS. 

gradually  into  the  night.  These  changes,  —  the 
glory,  the  death,  the  soft  succeeding  life, -^really 
seem  like  something  that  has  a  spiritual  exist- 
ence. While,  however,  I  counsel  my  friends  to 
see  the  Alps  for  the  first  time  in  the  afternoon, 
if  possible,  I  do  not  promise  them  that  the  hour 
will  bring  with  it  such  a  scene  as  I  have  tried  to 
describe.  Perfect  sunsets  are  rare  in  any  land ; 
but,  nevertheless,  I  would  advise  travellers  to 
choose  the  latter  half  of  the  day  and  a  road  over 
the  Jura  for  their  entrance  into  Switzerland.* 

It  was  from  the  Jura  itself  that  one  of  the 
great  epochs  in  the  history  of  the  globe  received 
its  name.  It  was  in  a  deep  gorge  of  the  Jura, 
that,  more  than  half  a  century  ago,  Leopold  von 
Buch  first  perceived  the  mode  of  formation  of 
mountains ;  and  it  was  at  the  foot  of  the  Jura, 

*  The  two  most  imposing  views  of  the  Alps  from  the  Jura 
are  those  of  Latourne,  on  the  road  from  Pontarlier  to  Neufcha- 
tel,  and  of  St.  Cergues,  on  the  road  from  Lons  le  Saulnier  to 
Nyon ;  the  next  best  is  to  be  had  above  Boujean,  on  the  road 
from  Basle  to  Bienne.  Very  extensive  views  may  be  obtained 
from  any  of  the  summits  in  the  southern  range  of  the  Jura; 
among  which  the  Weissenstein  above  Soleure,  the  Chasseral 
above  Bienne,  the  Chaumont  above  Neufchatel,  the  Chasseron 
above  Grancon,  the  Suchet  above  Orbe,  the  Mont  Tendre  or  the 
Noirmont  above  Morges,  and  the  Dole  above  Nyon,  are  the  most 
frequented.  Of  all  these  points  Chaumont  is  unquestionably  to 
be  preferred,  as  it  commands  at  the  same  time  an  equally  exten- 
sive view  of  the  Bernese  Alps  and  the  Mont  Blanc  range. 


THE  GROWTH  OF  CONTINENTS.       133 

in  the  neighborhood  of  Neufchatel,  that  the  in- 
vestigations were  made  which  first  led  to  the 
recognition  of  the  changes  connected  with  the 
Periods.  As  I  shall  have  occasion  hereafter  to 
enter  into  this  subject  more  at  length,  I  will  only 
allude  briefly  here  to  the  circumstances.  In  so 
doing  I  am  anticipating  the  true  geological  order, 
because  I  must  treat  of  the  Jurassic  and  Creta- 
ceous deposits,  which  are  still  far  in  advance  of  us  ; 
but  as  it  was  by  the  study  of  these  deposits  that 
the  circumscription  of  the  Periods,  as  I  have  de- 
fined them  above,  was  first  ascertained,  I  must 
allude  to  them  in  this  connection. 

Facing  the  range  of  the  Jura  from  the  Lake  of 
Neufcliatel,  there  seems  to  be  but  one  uninter- 
rupted slope  by  which  it  descends  to  the  shore  of 
the  lake.  It  will,  however,  be  noticed  by  the 
most  careless  observer  that  this  slope  is  divided 
by  the  difference  in  vegetation  into  two  strongly 
marked  bands  of  color:  the  lower  and  more 
gradual  descent  being  of  a  lighter  green,  while 
the  upper  portion  is  covered  by  the  deeper 
hue  of  the  forest-trees,  the  Beeches,  Birches,  Ma- 
ples, etc.,  above  which  come  the  Pines.  When 
the  vegetation  is  fully  expanded,  this  marked 
division  along  the  whole  side  of  the  range  into 
two  broad  bands  of  green,  the  lighter  below  and 
the  darker  above,  becomes  very  striking.  The 
lighter  band  represents  the  cultivated  portion  of 


134       THE  GROWTH  OF  CONTINENTS. 

the  slope,  the  vineyards,  the  farms,  the  orchards, 
covering  the  gentler,  more  gradual  part  of  the 
descent ;  and  the  whole  of  this  cultivated  tract, 
stretching  a  hundred  miles  east  and  west,  belongs 
to  the  Cretaceous  epoch.  The  upper  slope  of  the 
range,  where  the  forest-growth  comes  in,  is  Ju- 
rassic. Facing  the  range,  you  do  not,  as  I  have 
said,  perceive  any  difference  in  the  angle  of  in- 
clination ;  but  the  border-line  between  the  two 
bands  of  green  does  in  fact  mark  the  point  at 
which  the  Cretaceous  beds  abut  with  a  gentler 
slope  against  the  Jurassic  strata,  which  continue 
their  sharper  descent,  and  are  lost  to  view  be- 
neath them. 

This  is  one  of  the  instances  in  which  the  con- 
tact of  two  epochs  is  most  directly  traced.  There 
is  no  question,  from  the  relation  of  the  deposits, 
that  the  Jura  in  its  upheaval  carried  with  it  the 
strata  previously  accumulated.  At  its  base  there 
was  then  no  lake,  but  an  extensive  stretch  of 
ocean ;  for  the  whole  plain  of  Switzerland  was 
under  water,  and  many  thousand  years  elapsed 
before  the  Alps  arose  to  set  a  new  boundary  to 
the  sea  and  enclose  that  inland  sheet  of  water, 
gradually  to  be  filled  up  by  more  modern  accu- 
mulations, and  transformed  into  the  fertile  plain 
which  now  lies  between  the  Jura  and  the  Alps. 
If  the  reader  will  for  a  moment  transport  him- 
self in  imagination  to  the  time  when  the  south- 


THE  GEOWTH  OF  CONTINENTS.       135 

ern  side  of  the  Jurassic  range  sloped  directly 
down  to  the  ocean,  he  will  easily  understand  how 
this  second  series  of  deposits  was  collected  at  its 
base,  as  materials  are  collected  now  along  any 
sea-shore.  They  must  of  course  have  been  ac- 
cumulated horizontally,  since  no  loose  materials 
could  keep  their  place  even  at  so  moderate  an 
angle  as  that  of  the  present  lower  slope  of  the 
range ;  but  we  shall  see  hereafter  that  there  were 
many  subsequent  perturbations  of  this  region, 
and  that  these  Cretaceous  deposits,  after  they  had 
become  consolidated,  were  raised  by  later  upheav- 
als from  their  original  position  to  that  which 
they  now  occupy  on  the  lower  slope  of  the  Jura, 
resting  immediately,  but  in  geological  language 
unconformably ,  against  it.  The  two  adjoining 
wood-cuts  are  merely  theoretical,  showing  by 
lines  the  past  and  the  present  relation  of  these 
deposits ;  but  they  may  assist  the  reader  to  un- 
derstand my  meaning. 

Figure  1  rep- 
resents the  Jura 
before  the  Alps 
were  raised,  with 
the  Cretaceous 
deposits  accu- 
mulating  beneath  the  sea  at  its  base.  The  line 
marked  S  indicates  the  ocean-level ;  the  letter  c, 
the  Cretaceous  deposits ;  the  letter  y,  the  Juras- 
sic strata,  lifted  on  the  side  of  the  mountain. 


136       THE  GROWTH  OF  CONTINENTS. 

Figure  2  represents 
the  Jura  at  the  pres- 
ent time,  when  the 
latter  upheavals  have 
lifted  the  Jurassic 
strata  to  a  sharper 
inclination  with  the 
Cretaceous  deposits,  now  raised  and  forming  the 
lower  slope  of  the  mountain,  at  the  base  of  which 
is  the  Lake  of  Neufchatel,  marked  L  in  the  dia- 
gram. 

Although  this  change  of  inclination  is  hardly 
perceptible,  as  one  looks  up  against  the  face  of 
the  Jura  range,  there  is  a  transverse  cut  across 
it  which  seems  intended  to  give  us  a  diagram  of 
its  internal  structure.  Behind  the  city  of  Neuf- 
chatel rises  the  mountain  of  Chaumont,  so  called 
from  its  bald  head,  for  neither  tree  nor  shrub 
grows  on  its  summit.  Straight  through  this 
mountain,  from  its  northern  to  its  southern  side, 
there  is  a  natural  road,  formed  by  a  split  in  the 
mountain  from  top  to  bottom.  In  this  transverse 
cut,  which  forms  one  of  the  most  romantic  and 
picturesque  gorges  leading  into  the  heart  of  the 
Jura  range,  you  get  a  profile  view  of  the  change 
in  the  inclination  of  the  strata,  and  can  easily 
distinguish  the  point  of  juncture  between  the  two 
sets  of  deposits.  But  even  after  this  dislocation 
of  strata  had  been  perceived,  it  was  not  known 
that  it  indicated  the  commencement  of  a  new 


THE  GROWTH  OF  CONTINENTS.       137 

epoch,  and  it  is  here  that  my  own  share  in  the 
work,  such  as  it  is,  belongs. 

Accustomed  as  a  boy  to  ramble  about  in  the 
beautiful  gorges  and  valleys  of  the  Jura,  and  in 
riper  years,  as  my  interest  in  science  increased, 
to  study  its  formation  with  closer  attention,  this 
difference  in  the  inclination  of  the  slope  had  not 
escaped  my  observation.  I  was,  however,  still 
more  attracted  by  the  fossils  it  contained  than  by 
its  geological  character :  and,  indeed,  there  is  no 
better  locality  for  the  study  of  extinct  forms  of 
life  than  the  Jura.  In  all  its  breaks  and  ravines, 
wherever  the  inner  surface  of  the  rock  is  exposed, 
it  is  full  of  organic  remains  ;  and  to  take  a  hand- 
ful of  soil  from  the  roadside  is  often  to  gather  a 
handful  of  shells.  It  is  actually  built  of  the  re- 
mains of  animals,  and  there  are  no  coral  reefs  in 
existing  seas  presenting  a  better  opportunity  for 
study  to  the  naturalist  than  the  coral  reefs  of  the 
Jura.  Being  already  tolerably  familiar  with  the 
fossils  of  the  Jura,  it  occurred  to  me  to  compare 
those  of  the  upper  and  lower  slope ;  and  to  my 
surprise  I  found  that  they  were  everywhere  dif- 
ferent, and  that  those  of  the  lower  slope  were  in- 
variably Cretaceous  in  character,  while  those  of 
the  upper  slope  were  Jurassic.  In  the  course  of 
this  investigation  I  discovered  three  periods  in 
the  Cretaceous  and  four  in  the  Jurassic  epoch, 
all  characterized  by  different  fossils.  This  led  to 
a  more  thorough  investigation  of  the  different 


138       THE  GROWTH  OF  CONTINENTS. 

sets  of  strata,  resulting  in  the  establishment  by 
D'Orbigny  of  a  still  greater  number  of  periods, 
marked  by  the  successive  deposits  of  the  Jurassic 
and  Cretaceous  seas,  all  of  which  contained  dif- 
ferent organic  remains.  The  attention  of  geolo- 
gists being  once  turned  in  this  direction,  the 
other  epochs  were  studied  with  the  same  view, 
and  all  were  found  to  be  susceptible  of  division 
into  a  greater  or  less  number  of  such  periods. 

I  have  dwelt  at  greater  length  on  the  Jurassic 
and  Cretaceous  divisions,  because  I  believe  that 
we  have  in  the  relation  of  these  two  epochs,  as 
well  as  in  that  of  the  Cretaceous  epoch  with  the 
Tertiary  immediately  following  it,  facts  which 
are  very  important  in  their  bearing  on  certain 
questions,  now  loudly  discussed,  not  only  by  sci- 
entific men,  but  by  all  who  are  interested  in  the 
mode  of  origin  of  animals.  Certainly,  in  the  in- 
land seas  of  the  Cretaceous  and  subsequent  Ter- 
tiary times,  where  we  can  trace  in  the  same  sheet 
of  water  not  only  the  different  series  of  deposits 
belonging  to  two  successive  epochs  in  immediate 
juxtaposition,  but  those  belonging  to  all  the  pe- 
riods included  within  these  epochs,  with  the  or- 
ganic remains  contained  in  each,  —  there,  if  any- 
where, we  should  be  able  to  trace  the  transition- 
types  by  which  one  set  of  animals  is  said  to  have 
been  developed  out  of  the  preceding.  We  hear 
a  great  deal  of  the  interruption  in  geological  de- 
posits, of  long  intervals,  the  record  of  which  has 


THE  GROWTH  OF  CONTINENTS.       139 

vanished,  and  which  may  contain  those  interme- 
diate links  for  which  we  vainly  seek.  But  here 
there  is  no  such  gap  in  the  evidence.  In  the  very 
same  sheets  of  water,  covering  limited  areas,  we 
have  the  successive  series  of  deposits  containing 
the  remains  of  animals  which  continue  perfectly 
unchanged  during  long  intervals.  Immediately 
upon  these,  and  accompanied  by  a  more  or  less 
violent  shifting  of  the  surface,*  traceable  by  the 
consequent  discordance  of  the  strata,  is  intro- 
duced an  entirely  new  set  of  animals,  differing 
as  much  from  those  immediately  preceding  them 
as  do  those  of  the  present  period  from  the  older 
animals,  (our  predecessors,  but  not  our  ances- 
tors,) traced  by  Cuvier  in  the  Tertiary  deposits 
underlying  those  of  our  own  geological  age.  I 
subjoin  here  a  tabular  view  giving  the  Epochs  in 
their  relation  to  the  Ages,  and  indicating,  at 
least  approximately,  the  number  of  Periods  con- 
tained in  each  Epoch. 

Age  of  Man  Present  Epoch. 


f  Pliocene 

Tertiary  Age  : 

J  Miocene 

Age  of  Mammalia 

[Eocene 

f  Cretaceous 

Secondary  Age  : 

I  Jurassic 
J  Triassic 

Age  of  Reptiles 

Permian 

J  Carboniferous 

Pakeozoic  or  Primary  Age  : 

c  Devonian 

Age  of  Fishes 

/Silurian 

l 

C  witl1  about  twenty  Periods. 

ith  eight  or  nine  Periods. 


I  wi 
] 


*  I  use  surface  often  in  its  geological  significance,  meaning 
earth-crust,  and  applied  to  sea-bottom  as  well  as  to  dry  land. 


140      THE  GROWTH  OF  CONTINENTS. 

It  will  be  noticed  by  those  who  have  any  knowl- 
edge of  geological  divisions,  that  in  this  diagram 
I  consider  the  Carboniferous  epoch  as  forming  a 
part  of  the  Secondary  age.  Some  geologists  have 
been  inclined,  from  the  marked  and  peculiar 
character  of  its  vegetation,  to  set  it  apart  as  form- 
ing in  itself  a  distinct  geological  age,  while  oth- 
ers have  united  it  with  the  Palaeozoic  age.  For 
many  years  I  myself  adopted  the  latter  of  these 
two  views,  and  associated  the  Carboniferous  epoch 
with  the  Palaeozoic  age.  But  it  is  the  misfortune 
of  progress  that  one  is  forced  not  only  to  unlearn 
a  great  deal,  but,  if  one  has  been  in  the  habit  of 
communicating  his  ideas  to  others,  to  destroy 
much  of  his  own  work.  I  now  find  myself  in 
this  predicament ;  and  after  teaching  my  students 
for  years  that  the  Carboniferous  epoch  belongs  to 
the  Palaeozoic  or  Primary  age,  I  am  convinced,  — 
and  this  conviction  grows  upon  me  constantly  as 
I  free  myself  from  old  prepossessions  and  bias  on 
the  subject,  —  that  with  the  Carboniferous  epoch 
we  have  the  opening  of  the  Secondary  age  in  the 
history  of  the  world.  A  more  intimate  acquaint- 
ance with  organic  remains  has  shown  me  that 
there  is  a  closer  relation  between  the  character 
of  the  animal  and  vegetable  world  of  the  Carbo- 
niferous epoch,  as  compared  with  that  of  the  Per- 
mian and  Triassic  epochs,  than  between  that  of 
the  Carboniferous  epoch  and  any  preceding  one. 


THE  GROWTH  OF  CONTINENTS.       141 

Neither  do  I  see  any  reason  for  separating  it  from 
the  others  as  a  distinct  age.  The  plants  as  well 
as  the  animals  of  the  two  subsequent  epochs  seem 
to  me  to  show,  on  the  contrary,  the  same  pervad- 
ing character,  indicating  that  the  Carboniferous 
epoch  makes  an  integral  part  of  that  great  divis- 
ion which  I  have  characterized  as  the  Secondary 
age. 

"Within  the  Periods  there  is  a  still  more  limited 
kind  of  geological  division,  founded  upon  the 
special  character  of  local  deposits.  These  I 
would  call  geological  Formations,  indicating  con- 
crete local  deposits,  having  no  cosmic  character, 
but  circumscribed  within  comparatively  narrow 
areas,  as  distinguished  from  the  other  terms, 
Ages,  Epochs,  Periods,  which  have  a  more  uni- 
versal meaning,  and  are,  as  it  were,  cosmopolitan 
in  their  application.  Let  me  illustrate  my  mean- 
ing by  some  formations  of  the  present  time.  The 
accumulations  along  the  coast  of  Florida  are 
composed  chiefly  of  coral  sand,  mixed  of  course 
with  the  remains  of  the  animals  belonging  to  that 
locality ;  those  along  the  coast  of  the  Southern 
States  consist  principally  of  loam,  which  the  riv- 
ers bring  down  from  their  swamps  and  low,  mud 
dy  grounds  ;  those  upon  the  shores  of  the  Middle 
States  are  made  up  of  clay  from  the  disintegra- 
tion of  the  eastern  slopes  of  the  Alleghanies ; 
while  those  farther  north,  along  our  own  coast , 


142  THE  GROWTH  OF  CONTINENTS. 

are  mostly  formed  of  sand  from  the  New-England 
granites.  Such  deposits  are  the  local  work  of 
one  period,  containing  the  organic  remains  be- 
longing to  the  time  and  place.  From  the  geo- 
logical point  of  view,  I  would  call  them  Forma- 
tions ;  from  the  naturalist's  point  of  view  I  would 
call  them  Zoological  Provinces. 

Of  course,  in  urging  the  application  of  these 
names,  I  do  not  intend  to  assume  any  dictator- 
ship in  the  matter  of  geological  nomenclature. 
But  I  do  feel  very  strongly  the  confusion  arising 
from  an  indiscriminate  use  of  terms,  and  that, 
whatever  names  be  selected  as  most  appropriate 
or  descriptive  for  these  divisions,  geologists  should 
agree  to  use  them  in  the  same  sense. 

There  is  one  other  geological  term,  bequeathed 
to  us  by  a  great  authority,  and  which  cannot  be 
changed  for  the  better :  I  mean  that  of  Geologi- 
cal Horizon,  applied  by  Humboldt  to  the  whole 
extent  of  any  one  geological  division,  —  as,  for 
instance,  the  Silurian  horizon,  including  the 
whole  extent  of  the  Silurian  epoch.  It  indicates 
one  level  in  time,  as  the  horizon  which  limits  our 
view  indicates  the  farthest  extension  of  the  plain 
on  which  we  stand  in  space. 

We  left  America  at  the  close  of  the  Carbonif- 
erous epoch,  when  the  central  part  of  the  United 
States  was  already  raised  above  the  water.  Let 


THE  GKOWTH  OF  CONTINENTS.       143 

us  now  give  a  glance  at  Europe  in  those  early 
days,  and  see  how  far  her  physical  history  has 
advanced.  What  European  countries  loom  up 
for  us  out  of  the  Azoic  sea,  corresponding  in 
time  and  character  to  the  low  range  of  hills 
which  first  defined  the  northern  boundary  of  the 
United  States  ?  what  did  the  Silurian  and  Devo- 
nian epochs  add  to  these  earliest  tracts  of  dry 
land  in  the  Old  World  ?  and  where  do  we  find 
the  coal  basins  which  show  us  the  sites  of  her 
Carboniferous  forests?  Since  the  relation  be- 
tween the  epochs  of  comparative  tranquillity  and 
the  successive  upheavals  has  been  so  carefully 
traced  in  Europe,  I  will  endeavor,  while  giving  a 
sketch  of  that  early  European  world,  to  point  out, 
at  the  same  time,  the  connection  of  the  different 
systems  of  upheaval  with  the  successive  stratified 
deposits,  without,  however,  entering  into  such 
details  as  must  necessarily  become  technical  and 
tedious. 

In  the  European  ocean  of  the  Azoic  epoch  we 
find  five  islands  of  considerable  size.  The  largest 
of  these  is  at  the  North.  Scandinavia  had  even 
then  almost  her  present  outlines;  for  Norway, 
Sweden,  Finland,  and  Lapland,  all  of  which  are 
chiefly  granitic  in  character,  were  among  the  first 
lands  to  be  raised.  Between  Sweden  and  Nor- 
way there  is,  however,  still  a  large  tract  of  land 
under  water,  forming  an  extensive  lake  or  a  large 


144       THE  GROWTH  OF  CONTINENTS. 

inland  sea  in  the  heart  of  the  country.  If  the 
reader  will  take  the  trouble  to  look  on  any  geo- 
logical map  of  Europe,  he  will  see  an  extensive 
patch  of  Silurian  rock  in  the  centre  of  Sweden 
and  Norway.  This  represents  that  sheet  of  wa- 
ter gradually  to  be  filled  by  the  accumulation  of 
Silurian  deposits  and  afterwards  raised  by  a  later 
disturbance.  There  is  another  mas?  of  land  far 
to  the  southeast  of  this  Scandinavian  island, 
which  we  may  designate  as  the  Bohemian  island, 
for  it  lies  in  the  region  now  called  Bohemia, 
though  it  includes,  also,  a  part  of  Saxony  and 
Moravia.  The  northwest  corner  of  France,  that 
promontory  which  we  now  call  Bretagne,  with  a 
part  of  Normandy  adjoining  it,  formed  another 
island ;  while  to  the  southeast  of  it  lay  the  cen- 
tral plateau  of  France.  Great  Britain  was  not 
forgotten  in  this  early  world ;  for  a  part  of  the 
Scotch  hills,  some  of  the  Welsh  mountains,  and 
a  small  elevation  here  and  there  in  Ireland, 
already  formed  a  little  archipelago  in  that  region. 
By  a  most  careful  analysis  of  the  structure  of 
the  rocks  in  these  ancient  patches  of  land,  tracing 
all  the  dislocations  of  strata,  all  the  indications 
of  any  disturbance  of  the  earth-crust  whatsoever, 
Elie  de  Beaumont  has  detected  and  classified  four 
systems  of  upheavals,  previous  to  the  Silurian 
epoch,  to  which  he  refers  these  islands  in  the 
Azoic  sea.  He  has  named  them  the  systems  of 


THE  GEOWTH  OF  CONTINENTS.       145 

La  Vendee,  of  Finist£re,  of  Longmynd,  and  of 
Morbihan.  These  names  have,  for  the  present, 
only  a  local  significance,  —  being  derived,  like  so 
many  of  the  geological  names,  from  the  places 
where  the  investigations  of  the  phenomena  were 
first  undertaken  ;  but  in  course  of  time  they  will, 
no  doubt,  apply  to  all  the  contemporaneous  up- 
heavals, wherever  they  may  be  traced,  just  as  we 
now  have  Silurian,  Devonian,  Permian,  and  Ju- 
rassic deposits  in  America  as  well  as  in  Europe. 

The  Silurian  and  Devonian  epochs  seem  to 
have  been  instrumental  rather  in  enlarging  the 
tracts  of  land  already  raised  than  in  adding  new 
ones ;  yet  to  these  two  epochs  is  traced  the  up- 
heaval of  a  large  and  important  island  to  the 
northeast  of  France.  We  may  call  it  the  Bel- 
gian island,  since  it  covered  the  ground  of  mod- 
ern Belgium ;  but  it  also  extended  considerably 
beyond  these  limits,  and  included  much  of  the 
Northern  Rhine  region.  A  portion  only  of  this 
tract,  to  which  belongs  the  central  mass  of  the 
Vosges  and  the  Black  Forest,  was  lifted  during 
the  Silurian  epoch,  —  which  also  enlarged  con- 
siderably Wales  and  Scotland,  the  Bohemian 
island,  the  island  of  Bretagne,  and  Scandinavia. 
During  this  epoch  the  sheet  of  water  between 
Norway  and  Sweden  became  dry  land,  a  consid- 
erable tract  was  added  to  their  northern  extrem- 
ity on  the  Arctic  shore ;  while  a  broad  band  of 


146       THE  GROWTH  OF  CONTINENTS. 

Silurian  deposits,  lying  now  between  Finland  and 
Russia,  enlarged  that  region. 

The  Silurian  epoch  has  been  referred  by  Elie 
de  Beaumont  to  the  system  of  upheaval  called  by 
him  the  system  of  Westmoreland  and  Hunds- 
riick,  —  again  merely  in  reference  to  the  spots  at 
which  these  upheavals  were  first  studied,  the  cen- 
tres, as  it  were,  from  which  the  investigations 
spread.  But  in  their  geological  significance  they 
indicate  all  the  oscillations  and  disturbances  of 
the  soil  throughout  the  region  over  which  the 
Silurian  deposits  have  been  traced  in  Europe. 
The  Devonian  epoch  added  greatly  to  the  out- 
lines of  the  Belgian  island.  To  it  belongs  the 
region  of  the  Ardennes,  lying  between  France 
and  Belgium,  the  Eifelgebirge,  and  a  new  dis- 
turbance of  the  Yosges,  by  which  that  region  was 
also  extended.  The  island  of  Bretagne  was 
greatly  increased  by  the  Devonian  deposits,  and 
Bohemia  gained  in  dimensions,  while  the  central 
plateau  of  France  remained  much  the  same  as 
before.  The  changes  of  the  Devonian  epoch  are 
traced  by  Elie  de  Beaumont  to  a  system  of  up- 
heavals called  the  Ballons  of  the  Vosges  and  of 
Normandy,  —  so  called  from  the  rounded,  bal- 
loon-like domes  characteristic  of  the  mountains 
of  that  time.  To  the  Carboniferous  epoch  be- 
long the  mountain-systems  of  Forey,  (to  the  west 
of  Lyons,)  of  the  North  of  England,  and  of  the 


THE  GROWTH  OF  CONTINENTS.      147 

Netherlands.  These  three  systems  of  upheaval 
have  also  been  traced  by  Elie  de  Beaumont ;  and 
in  the  depressions  formed  between  their  eleva- 
tions we  find  the  coal-basins  of  Central  France, 
of  England,  and  of  Germany.  During  all  these 
epochs,  in  Europe  as  in  America,  every  such  dis- 
location of  the  surface  was  attended  by  a  change 
in  the  animal  creation. 

If  we  take  now  a  general  view  of  the  aspect 
of  Europe  at  the  close  of  the  Carboniferous 
epoch,  we  shall  see  that  the  large  island  of  Scan- 
dinavia is  completed,  while  the  islands  of  Bohe- 
mia and  Belgium  have  approached  each  other  by 
their  gradual  increase  till  they  are  divided  only 
by  a  comparatively  narrow  channel.  The  island 
of  Belgium,  that  of  Bretagne,  and  that  of  the 
central  plateau  of  France,  form  together  a  tri- 
angle, of  which  the  plateau  is  the  lowest  point, 
while  Belgium  and  Bretagne  form  the  other  two 
corners.  Between  the  plateau  and  Belgium  flows 
a  channel,  which  we  may  call  the  Burgundian 
channel,  since  it  covers  old  Burgundy ;  between 
the  plateau  and  Bretagne  is  another  channel, 
which  from  its  position  we  may  call  the  Bordeaux 
channel.  The  space  inclosed  between  these  three 
masses  of  land  is  filled  by  open  sea.  To  trace 
the  gradual  closing  of  these  channels  and  the 
filling  up  of  the  ocean  by  constantly  increasing 
accumulations,  as  well  as  by  upheavals,  will  be 
the  object  of  the  next  article. 


VI. 

THE  GEOLOGICAL  MIDDLE  AGE. 

I  SHALL  pass  lightly  over  the  Permian  and 
Triassic  epochs,  as  being  more  nearly  related 
in  their  organic  forms  to  the  Carboniferous  epoch, 
with  which  we  are  already  somewhat  familiar, 
while  in  those  next  in  succession,  the  Jurassic 
and  Cretaceous  epochs,  the  later  conditions  of 
anim'al  life  begin  to  be  already  foreshadowed. 
But  though  less  significant  for  us  in  the  present 
stage  of  our  discussion,  it  must  not  be  supposed 
that  the  Permian  and  Triassic  epochs  were  unim- 
portant in  the  physical  and  organic  history  of 
Europe.  A  glance  at  any  geological  map  of 
Europe  will  show  the  reader  how  the  Belgian 
island  stretched  gradually  in  a  southwesterly 
direction  during  the  Permian  epoch,  approaching 
the  coast  of  France  by  slowly  increasing  accumu- 
lations, and  thus  filling  the  Burgundian  channel ; 
a  wide  border  of  Permian  deposits  around  the 
coal-field  of  Great  Britain  marks  the  increase  of 
this  region  also  during  the  same  time,  and  a  very 
extensive  tract  of  a  like  character  is  to  be  seen  in 


THE   GEOLOGICAL  MIDDLE  AGE.  149 

Russia.  The  latter  is,  however,  still  under  doubt 
and  discussion  among  geologists,  and  more  recent 
investigations  tend  to  show  that  this  Russian  re- 
gion, supposed  at  first  to  be  exclusively  Permian, 
is  in  part  at  least,  Triassic. 

With  the  coming  in  of  the  Triassic  epoch  be- 
gan the  great  deposits  of  Red  Sandstone,  Mu- 
schel-Kalk,  and  Keuper,  in  Central  Europe.  They 
united  the  Belgian  island  to  the  region  of  the 
Yosges  and  the  Black  Forest,  while  they  also 
filled  to  a  great  extent  the  c'hannel  between  Bel- 
gium and  the  Bohemian  island.  Thus  the  land 
slowly  gained  upon  the  Triassic  ocean,  shutting 
it  within  ever-narrowing  limits,  and  preparing 
the  large  inland  seas  so  characteristic  of  the  later 
Secondary  times. 

The  character  of  the  organic  world  still  re- 
tained a  general  resemblance  to  that  of  the  Car- 
boniferous epoch.  Among  Radiates,  the  Corals 
were  more  nearly  allied  to  those  of  the  earlier 
ages  than  to  those  of  modern  times,  and  Crinoids 
abounded  still,  though  some  of  the  higher  Echi- 
noderm  types  were  already  introduced.  Among 
Mollusks,  the  lower  Bivalves,  that  is,  the  Brachio- 
pods  and  Bryozoa,  still  prevailed,  while  Ammon- 
ites continued  to  be  very  numerous,  differing 
from  the  earlier  ones  chiefly  in  the  ever-increas- 
ing complications  of  their  inner  partitions,  which 
become  so  deeply  involuted  and  cut  upon  their 


150  THE  GEOLOGICAL  MIDDLE  AGE. 

margins,  before  the  type  disappears,  as  to  make 
an  intricate  tracery  of  very  various  patterns  on 
the  surface  of  these  shells.  The  most  conspicu- 
ous type  of  Articulates  continues  as  before  to  be 
that  of  Crustacea;  but  Trilobites  have  finished 
their  career,  and  the  Lobster-like  Crustacea  make 
their  appearance  for  the  first  time.  It  does  not 
seem  that  the  class  of  Insects  has  greatly  in- 
creased since  the  Carboniferous  epoch ;  and 
Worms  are  still  as  difficult  to  trace  as  ever,  be- 
ing chiefly  known  by  the  cases  in  which  they 
sheltered  themselves.  Among  Vertebrates,  the 
Fishes  still  resemble  those  of  the  Carboniferous 
epoch,  belonging  principally  to  the  Selachians 
and  Ganoids.  They  have,  however,  approached 
somewhat  toward  a  modern  pattern,  the  lobes  of 
the  tail  being  more  evenly  cut,  and  their  general 
outline  more  like  that  of  common  fishes.  The 
gigantic  marsh  Reptiles  have  become  far  more 
numerous  and  various.  They  continue  through 
several  epochs,  but  may  be  said  to  reach  their 
culminating  point  in  the  Jurassic  and  Cretaceous 
deposits. 

I  cannot  pass  over  the  Triassic  epoch  without 
some  allusion  to  the  so-called  bird-tracks,  so  gen- 
erally believed  to  mark  the  introduction  of  Birds 
at  this  time.  It  is  true  that  in  the  deposits  of 
the  Trias  there  have  been  found  many  traces  of 
footsteps,  indicating  a  vast  number  of  animals 


THE   GEOLOGICAL  MIDDLE  AGE.  151 

which,  except  for  these  footprints,  remain  un- 
known to  us.  In  the  sandstone  of  the  Connecti- 
cut Valley  they  are  found  in  extraordinary  num- 
bers, as  if  these  animals,  whatever  they  were, 
had  been  in  the  habit  of  frequenting  that  shore. 
They  appear  to  have  been  very  diversified ;  for 
some  of  the  tracks  are  very  large,  others  quite 
small,  while  some  would  seem,  from  the  way  in 
which  the  footsteps  follow  each  other,  to  have 
been  quadrupedal,  and  others  bipedal.  We  can 
even  measure  the  length  of  their  strides,  follow- 
ing the  impressions  which,  from  their  succession 
in  a  continuous  line,  mark  the  walk  of  a  single 
animal.*  The  fact  that  we  find  these  footprints 
without  any  bones  or  other  remains  to  indicate 
the  animals  by  which  they  were  made  is  ac- 
counted for  by  the  mode  of  deposition  of  the 
sandstone.  It  is  very  unfavorable  for  the  preser- 
vation of  bones ;  but,  being  composed  of  minute 
sand  mixed  with  mud,  it  affords  an  admirable 
substance  for  the  reception  of  these  impressions, 
which  have  been  thus  cast  in  a  mould,  as  it  were, 
and  preserved  through  ages. 

These  animals  must  have  been  large,  when 
full-grown,  for  we  find  strides  measuring  six  feet 
between,  evidently  belonging  to  the  same  animal. 
In  the  quadrupedal  tracks,  the  front  seem  to  have 

*  For  all  details  respecting  these  tracks  see  Hitchcock's  Ich- 
nology  of  New  England.  Boston,  1858.  4to. 


152  THE   GEOLOGICAL  MIDDLE  AGE. 

been  smaller  than  the  hind  ones.  Some  of  the 
tracks  show  four  toes  all  turned  forward,  while 
in  others  three  toes  are  turned  forward  and  one 
backward.  It  happened  that  the  first  tracks 
found  belonged  to  the  latter  class  ;  and  they  very 
naturally  gave  rise  to  the  idea  that  these  impres- 
sions were  made  by  birds,  on  account  of  this  for- 
mation of  the  foot.  This,  however,  is  a  mere  in- 
ference ;  and  since  the  inductive  method  is  the 
only  true  one  in  science,  it  seems  to  me  that  we 
should  turn  to  the  facts  we  have  in  our  possession 
for  the  explanation  of  these  mysterious  footprints, 
rather  than  endeavor  to  supply  by  assumption 
those  which  we  have  not.  As  there  are  no  bones 
found  in  connection  with  these  tracks,  the  only 
way  to  arrive  at  their  true  character,  in  the  pre- 
sent state  of  our  knowledge,  is  by  comparing 
them  with  bones  found  in  other  localities  in  the 
deposits  of  the  same  period  in  the  world's  history. 
Now  there  have  never  been  found  in  the  Trias 
any  remains  of  Birds,  while  it  contains  innumer- 
able bones  of  Reptiles ;  and  therefore  I  think  that 
we  shall  eventually  find  the  solution  of  this  mys- 
tery in  the  latter  class. 

It  is  true  that  the  bones  of  the  Triassic  Reptiles 
are  scattered  and  disconnected ;  *  no  complete 
skeleton  has  yet  been  discovered,  nor  has  any  foot 

*  See  the  Investigations  of  Hermann  von  Meyer  on  Triassic 
Keptiles. 


THE   GEOLOGICAL  MIDDLE  AGE.  153 

been  found  ;  so  that  no  direct  comparison  can  be 
made  with  the  steps.  It  is,  however,  my  belief, 
from  all  we  know  of  the  character  of  the  Animal 
Kingdom  in  those  days,  that  these  animals  were 
reptilian,  but  combined,  like  so  many  of  the  early 
types,  characters  of  their  own  class  with  those  of 
higher  animals  yet  to  come.  It  seems  to  me  prob- 
able, that,  in  those  tracks  where  one  toe  is  turned 
backward,  the  impression  is  made  not  by  a  toe, 
but  by  a  heel,  or  by  a  long  sole  projecting  back- 
ward; for  it  is  not  pointed,  like  those  of  the  front 
toes,  but  is  blunt.  It  is  true  that  there  is  a  divi- 
sion of  joints  in  the  toes,  which  seems  in  favor  of 
the  idea  that  they  were  those  of  Birds  ;  for  when 
the  three  toes  are  turned  forward,  there  are  two 
joints  on  the  inner  one,  three  on  the  middle,  and 
four  on  the  outer  one,  as  in  Birds.  But  this  fea- 
ture is  not  peculiar  to  Birds ;  it  is  found  in  Tur- 
tles also.  The  correspondence  of  these  footprints 
with  each  other  leaves  no  doubt  that  they  were  all 
by  one  kind  of  animal ;  for  both  the  bipedal  and 
the  quadrupedal  tracks  have  the  same  character. 
The  only  quadrupedal  animals  now  known  to  us 
which  walk  on  two  legs  are  the  Kangaroos.  They 
raise  themselves  on  their  hind  legs,  using  the 
front  ones  to  bring  their  food  to  their  mouth. 
They  leap  with  the  hind  legs,  sometimes  bring- 
ing down  their  front  feet  to  steady  themselves 
after  the  spring,  and  making  use  also  of  their 

7* 


154  THE   GEOLOGICAL  MIDDLE  AGE. 

tails,  to  balance  the  body  after  leaping.  In  these 
tracks  we  find  traces  of  a  tail  between  the  feet. 
I  do  not  bring  this  forward  as  any  evidence  that 
these  animals  were  allied  to  Kangaroos,  since  I 
believe  that  nothing  is  more  injurious  in  science 
than  assumptions  which  do  not  rest  on  a  broad 
basis  of  facts ;  but  I  wish  only  to  show  that  these 
tracks  recall  other  animals  besides  Birds,  with 
which  they  have  been  universally  associated. 
And  seeing,  as  we  do,  that  so  many  of  the  early 
types  prophesy  future  forms,  it  seems  not  improb- 
able that  they  may  have  belonged  to  animals 
which  combined  with  reptilian  characters  some 
birdlike  features,  and  also  some  features  of  the 
earliest  and  lowest  group  of  Mammalia,  the  Mar- 
supials. To  sum  up  my  opinion  respecting  these 
footmarks,  I  believe  that  they  were  made  by  ani- 
mals of  a  prophetic  type,  belonging  to  the  class 
of  Reptiles,  and  exhibiting  many  synthetic  char- 
acters. 

The  more  closely  we  study  past  creations,  the 
more  impressive  and  significant  do  the  synthetic 
types,  presenting  features  of  the  higher  classes 
under  the  guise  of  the  lower  ones,  become.  They 
.hold  the  promise  of  the  future.  As  the  opening 
overture  of  an  opera  contains  all  the  musical  ele- 
ments to  be  therein  developed,  so  this  living  pre- 
lude of  the  Creative  work  comprises  all  the  or- 
ganic elements  to  be  successively  developed  in 


THE   GEOLOGICAL   MIDDLE  AGE.  155 

the  course  of  time.  When  Cuvier  first  saw  the 
teeth  of  a  Wealden  Reptile,  he  pronounced  them 
to  be  those  of  a  Rhinoceros,  so  mammalian  were 
they  in  their  appearance.  So,  when  Sommering 
first  saw  the  remains  of  a  Jurassic  Pterodactyl, 
he  pronounced  them  to  be  those  of  a  Bird.  These 
mistakes  were  not  due  to  a  superficial  judgment 
in  men  who  knew  Nature  so  well,  but  to  this  pro- 
phetic character  in  the  early  types  themselves,  in 
which  features  were  united  never  known  to  exist 
together  in  our  days,  and  presenting  a  kind  of 
combination  wholly  new  to  scientific  men  at  that 
time. 

The  Jurassic  epoch,  next  in  succession,  was  a 
very  important  one  in  the  history  of  Europe.  It 
completed  the  junction  of  several  of  the  larger 
islands,  filling  the  channel  between  the  central 
plateau  of  France  and  the  Belgian  island,  as  well 
as  that  between  the  former  and  the  island  of  Bre- 
tagne,  so  that  France  was  now  a  sort  of  crescent 
of  land  holding  a  Jurassic  sea  in  its  centre,  Bre- 
tagne  and  Belgium  forming  the  two  horns.  This 
Jurassic  basin  or  inland  sea  united  England  and 
France,  and  it  may  not  be  amiss  to  say  a  word 
here  of  its  subsequent  transformations.  During 
the  long  succession  of  Jurassic  periods,  the  depos- 
its of  that  epoch,  chiefly  limestone  and  clays,  with 
here  and  there  a  bed  of  sand,  were  accumulated 


156  THE   GEOLOGICAL   MIDDLE  AGE. 

at  its  bottom.  Upon  these  followed  the  chalk  de- 
posits of  the  Cretaceous  epoch,  until  the  basin 
was  gradually  filled,  and  partially,  at  least,  turned 
to  dry  land.  But  at  the  close  of  the  Cretaceous 
epoch  a  fissure  was  formed,  allowing  the  entrance 
of  the  sea  at  the  western  end,  so  that  the  con- 
stant washing  of  the  tides  and  storms  wore  away 
the  lower,  softer  deposits,  leaving  the  overhang- 
ing chalk  cliffs  unsupported.  These  latter,  as 
their  supports  were  undermined,  crumbled  down, 
thus  widening  the  channel  gradually.  This  pro- 
cess must,  of  course,  have  gone  on  more  rapidly 
at  the  western  end,  where  the  sea  rushed  in  with 
most  force,  till  the  channel  was  worn  through  to 
the  German  Ocean  on  the  other  side,  and  the  sea 
then  began  to  act  with  like  power  at  both  ends  of 
the  channel.  This  explains  its  form,  wider  at 
the  western  end,  narrower  between  Dover  and 
Calais,  and  widening  again  at  the  eastern  ex- 
tremity. This  ancient  basis,  extending  from  the 
centre  of  France  into  England,  is  rich  in  the  re- 
mains of  a  number  of  successive  epochs.  Around 
its  margin  we  find  the  Jurassic  deposits,  showing 
that  there  must  have  been  some  changes  of  level 
which  raised  the  shores  and  prevented  later  ac- 
cumulations from  covering  them,  while  in  the 
centre  the  Jurassic  deposits  are  concealed  by 
those  of  the  Cretaceous  epoch  above  them,  these 
being  also  partially  hidden  under  the  later  Ter- 


THE   GEOLOGICAL  MIDDLE  AGE.  15T 

tiary  beds.  Let  us  see,  then,  what  this  inland 
sea  has  to  tell  us  of  the  organic  world  in  the 
Jurassic  epoch. 

At  that  time  the  region  where  Lyme-Regis  is 
now  situated  in  modern  England  was  an  estuary 
on  the  shore  of  that  ancient  sea.  About  fifty 
years  ago  a  discovery  of  large  and  curious  bones, 
belonging  to  some  animal  unknown  to  the  scien- 
tific world,  turned  the  attention  of  naturalists  to 
this  locality,  and  since  then  such  a  quantity  and 
variety  of  such  remains  have  been  found  in  that 
neighborhood  as  to  show  that  the  Sharks,  Whales, 
Porpoises,  etc.,  of  the  present  ocean  are  not  more 
numerous  and  diversified  than  were  the  inhabi- 
tants of  this  old  bay  or  inlet.  Among  these  ani- 
mals, the  Ichthyosauri  (Fish-Lizards)  form  one 
of  the  best-known  and  most  prominent  groups. 
They  are  chiefly  found  in  the  Lias,  the  lowest  set 
of  beds  of  the  Jurassic  deposits,  and  seem  to  have 
come  in  with  the  close  of  the  Triassic  epoch.  It 
is  greatly  to  be  regretted  that  whatever  is  known 
of  the  Triassic  Reptiles  antecedent  to  the  Ichthy- 
osauri still  remains  in  the  form  of  original  papers, 
and  is  not  yet  embodied  in  text-books.  They  are 
quite  as  interesting,  as  curious,  and  as  diversified 
as  those  of  the  Jurassic  epoch,  which  are,  how- 
ever, much  more  extensively  known,  on  account 
of  the  large  collections  of  these  animals  belong- 
ing to  the  British  Museum.  It  will  be  more  easy 


158  THE   GEOLOGICAL  MIDDLE   AGE. 

to  understand  the  structural  relations  of  the  lat- 
ter, and  their  true  position  in  the  Animal  King- 
dom, when  those  which  preceded  them  are  better 
understood.  One  of  the  most 
remarkable  and  numerous  of 
these  Triassic  Reptiles  seems  to 
have  been  an  animal  called  La- 
byrinthodon,  and  resembling,  in 
the  form  of  the  head,  and  in 
the  two  articulating  surfaces  at 
the  juncture  of  the  head  with 
the  backbone,  the  Frogs  and 
Salamanders,  though  its  teeth 
are  like  those  of  a  Crocodile. 
As  yet  nothing  has  been  found 
of  these  animals  except  the 
head,  —  neither  the  backbone 
nor  the  limbs ;  so  that  little  is 
known  of  their  general  struct- 
ure. 

The  Ichthyosauri  (Figure  1) 
must    have    been    very    large, 
seven  or  eight  feet  being  the 
ordinary    length,    while    speci- 
mens  measuring  from  twenty 
to  thirty  feet  are  not  uncom- 
mon.    The  large  head  is  pointed,  like  that  of  the 
Porpoise ;  the  jaws  contain  a  number  of  conical 
teeth,  of  reptilian  form  and  character ;  the  eye- 


THE   GEOLOGICAL  MIDDLE   AGE.  159 

ball  was  very  large,  as  may  be  seen  by  the  socket, 
and  it  was  supported  by  pieces  of  bone,  such  as 
we  find  now  only  in  the  eyes  of  birds  of  prey  and 
in  the  bony  fishes.  The  ribs  begin  at  the  neck 
and  continue  to  the  tail,  and  there  is  no  distinc- 
tion between  head  and  neck,  as  in  most  Reptiles, 
but  a  continuous  outline,  as  in  Fishes.  They  had 
four  limbs,  not  divided  into  fingers,  but  forming 
mere  paddles.  Yet  fingers  seem  to  be  hinted  at 
in  these  paddles,  though  not  developed,  for  the 
bones  are  in  parallel  rows,  as  if  to  mark  what 
might  be  such  a  division.  The  backbones  are 
short,  but  very  high,  and  the  surfaces  of  articula- 
tion are  hollow,  conical  cavities,  as  in  Fishes,  in- 
stead of  ball-and-socket  joints,  as  in  Reptiles. 
The  ribs  are  more  complicated  than  in  Verte- 
brates generally:  they  consist  of  several  pieces, 
and  the  breast-bone  is  formed  of  a  number  of 
bones,  making  together  quite  an  intricate  bony 
network.  There  is  only  one  living  animal,  the 
Crocodile,  characterized  by  this  peculiar  struct- 
ure of  the  breast-bone.  The  Ichthyosaurus  is, 
indeed,  one  of  the  most  remarkable  of  the  syn- 
thetic types :  by  the  shape  of  its  head  one  would 
associate  it  with  the  Porpoises,  while  by  its  pad- 
dles and  its  long  tail  it  reminds  one  of  the  whole 
group  of  Cetaceans  to  which  the  Porpoises  be- 
long ;  by  its  crocodilian  teeth,  its  ribs,  and  its 
breast-bone,  it  seems  allied  to  Reptiles;  and  by 


160 


THE   GEOLOGICAL  MIDDLE  AGE. 


its  uniform  neck,  not  distinguished  from  the 
body,  and  the  structure  of  the  backbone,  it  re- 
calls the  Fishes. 

Another  most  curious  member  of  this  group  is 


Fig.  2. 


the  Plesiosaurus,  old  Saurian  (Figure  2).    By  its 
disproportionately  long  and  flexible  neck,  and  its 


THE   GEOLOGICAL  MIDDLE  AGE.  161 

small,  flat  head,  it  unquestionably  foreshadows 
the  Serpents,  while  by  the  structure  of  the  back- 
bone, the  limbs,  and  the  tail,  it  is  closely  allied 
with  the  Ichthyosaurus.  Its  flappers  are,  however, 
more  slender,  less  clumsy,  and  were,  no  doubt, 
adapted  to  more  rapid  motion  than  the  fins  of  the 
Ichthyosaurus,  while  its  tail  is  shorter  in  propor- 
tion to  the  whole  length  of  the  animal.  It  seems 
probable,  from  its  general  structure,  that  the 
Ichthyosaurus  moved  like  a  Fish,  chiefly  by  the 
flapping  of  the  tail,  aided  by  the  fins,  while  in  the 
Plesiosaurus  the  tail  must  have  been  much  less 
efficient  as  a  locomotive  organ,  and  the  long, 
snake-like,  flexible  neck  no  doubt  rendered  the 
whole  body  more  agile  and  rapid  in  its  move- 
ments. In  comparing  the  two,  it  may  be  said, 
that,  as  a  whole,  the  Ichthyosaurus,  though  be- 
longing by  its  structure  to  the  class  of  Reptiles, 
has  a  closer  external  resemblance  to  the  Fishes, 
while  the  Plesiosaurus  is  more  decidedly  reptilian 
in  character.  If  there  exists  any  animal  in  our 
waters,  not  yet  known  to  naturalists,  answering 
to  the  descriptions  of  the  "  Sea-Serpent,"  it  must 
be  closely  allied  to  the  Plesiosaurus.  The  occur- 
rence in  the  fresh  waters  of  North  America  of  a 
Fish,  the  Lepidosteus,  which  is  closely  allied  to 
the  fossil  Fishes  found  with  the  Plesiosaurus  in 
the  Jurassic  beds,  renders  such  a  supposition 
probable. 


162 


THE   GEOLOGICAL  MIDDLE  AGE. 


Of  all  these  strange  old  forms,  so  singularly 
uniting  features  of  Fishes  and  Reptiles,  none  has 
given  rise  to  more  discusion  than  the  Pterodacty- 
lus,  (Figure  3,)  another  of  the  Saurian  tribe, 


associated,  however,  with  Birds  by  some  natural- 
ists, on  account  of  its  large  wing-like  appendages. 
From  the  extraordinary  length  of  its  anterior 
limbs,  they  have  generally  been  described  as 
wings,  and  the  animal  is  usually  represented  as 


THE   GEOLOGICAL  MIDDLE  AGE.  163 

a  flying  Reptile.  But  if  we  consider  its  whole 
structure,  this  does  not  seeni  probable,  and  I  be- 
lieve it  to  have  been  an  essentially  aquatic  ani- 
mal, moving  after  the  fashion  of  the  Sea-Turtle. 
Its  so-called  wings  resemble  in  structure  the  front 
paddles  of  the  Sea-Turtles  far  more  than  the 
wings  of  a  Bird ;  differing  from  them,  indeed, 
only  by  the  extraordinary  length  of  the  inner 
toe,  while  the  outer  ones  are  comparatively  much 
shorter.  But,  notwithstanding  this  difference, 
the  hand  of  the  Pterodactylus  is  constructed  like 
that  of  an  aquatic  swimming  marine  Reptile  ;  and 
I  believe,  that,  if  we  represent  it  with  its  long 
neck  stretched  upon  the  water,  its  large  head 
furnished  with  powerful,  well-armed  jaws,  ready 
to  dive  after  the  innumerable  smaller  animals 
living  in  the  same  ocean,  we  shall  have  a  more 
natural  picture  of  its  habits  than  if  we  consider 
it  as  a  flying  animal,  which  it  is  generally  sup- 
posed to  have  been.  It  has  not  the  powerful 
breast-bone,  with  the  large  projecting  keel  along 
the  middle  line,  such  as  exists  in  all  the  flying 
animals.  Its  breast-bone,  on  the  contrary,  is  thin 
and  flat,  like  that  of  the  present  Sea-Turtle ;  and 
if  it  moved  through  the  water  by  the  help  of  its 
long  flappers,  as  the  Sea-Turtle  does  now,  it  could 
well  dispense  with  that  powerful  construction  of 
the  breast-bone  so  essential  to  all  animals  which 
fly  through  the  air.  Again,  the  powerful  teeth, 


164  THE   GEOLOGICAL  MIDDLE  AGE. 

long  and  conical,  placed  at  considerable  intervals 
in  the  jaw,  constitute  a  feature  common  to  all 
predaceous  acquatic  animals,  and  would  seem  to 
have  been  utterly  useless  in  a  flying  animal  at 
that  time,  since  there  were  no  aerial  beings  of 
any  size  to  prey  upon.  The  Dragon-Flies  found 
in  the  same  deposits  with  the  Pterodactylus  were 
certainly  not  a  game  requiring  so  powerful  a  bat- 
tery of  attack. 

The  Fishes  of  the  Jurassic  sea  were  exceedingly 
numerous,  but  were  all  of  the  Ganoid  and  Se- 
lachian tribes.  It  would  weary  the  reader,  were 
I  to  introduce  here. any  detailed  description  of 
them,  but  they  were  as  numerous  and  varied  as 
those  living  in  our  present  waters.  There  was 
the  Hybodus,  with  the  marked  furrows  on  the 
spines  and  the  strong  hooks  along  their  margin, 
—  the  huge  Chimera,  with  its  long  whip,  its 
curved  bone  over  the  back,  and  its  parrot-like 
bill, —  the  Lepidotus,  with  its  large  square  scales, 
its  large  head,  its  numerous  rows  of  teeth,  one 
within  another,  forming  a  powerful  grinding  ap- 
paratus,—  the  Microdon,  with  its  round,  flat 
body,  its  jaw  paved  with  small  grinding  teeth,  — 
the  swift  Aspidorhynchus,  with  its  long,  slender 
body  and  massive  tail,  enabling  it  to  strike  the 
water  powerfully  and  dart  forward  with  great  ra- 
pidity. There  were  also  a  host  of  small  Fishes, 
comparing  with  those  above  mentioned  as  our 


THE   GEOLOGICAL  MIDDLE  AGE.  165 

Perch,  Herring,  Smelts,  etc.,  compare  with  our 
larger  Fishes ;  but,  whatever  their  size  or  form, 
all  the  Fishes  of  those  days  had  the  same  hard 
scales  fitting  to  each  other  by  hooks,  instead  of 
the  thin  membranous  scales  overlapping  each 
other  at  the  edge,  like  the  common  Fishes  of 
more  modern  times.  The  smaller  Fishes,  no 
doubt,  afforded  food  to  the  larger  ones,  and  to 
the  aquatic  Reptiles.  Indeed,  in  parts  of  the  in- 
testines of  the  Ichthyosauri,  and  in  their  petrified 
excrements,  have  been  found  the  scales  and  teeth 
of  these  smaller  Fishes  perfectly  preserved.  It  is 
amazing  that  we  can  learn  so  much  of  the  habits 
of  life  of  these  past  creatures,  and  know  even 
what  was  the  food  of  animals  existing  countless 
ages  before  man  was  created. 

There  are  traces  of  Mammalia  in  the  Jurassic 
deposits,  but  they  were  of  those  inferior  kinds 
known  now  as  Marsupials,  and  no  complete  speci- 
mens have  yet  been  found. 

The  Articulates  were  largely  represented  in 
this  epoch.  There  were  already  in  the  vegetation 
a  number  of  Gymnosperms,  affording  more  favor- 
able nourishment  for  Insects  than  the  forests  of 
earlier  times ;  and  we  accordingly  find  that  class 
in  larger  numbers  than  ever  before,  though  still 
meagre  in  comparison  with  its  present  represen- 
tation. Crustacea  were  numerous,  —  those  of 
the  Shrimp  and  Lobster  kinds  prevailing,  though 


166  THE   GEOLOGICAL  MIDDLE  AGE. 

in  some  of  the  Lobsters  we  have  the  first  advance 
towards  the  highest  class  of  Crustacea  in  the  ex- 
pansion of  the  transverse  diameter  now  so  charac- 
teristic of  the  Crabs.  Among  Mollusks  we  have 
a  host  of  gigantic  Ammonites  ;  and  the  naked 
Cephalopods,  which  were  in  later  times  to  become 
the  prominent  representatives  of  that  class,  al- 
ready begin  to  make  their  appearance.  Among 
Radiates,  some  of  the  higher  kinds  of  Echino- 
derms,  the  Ophiurans,  and  Echinoids,  take  the 
place  of  the  Crinoids,  and  the  Acalephian  Corals 
give  way  to  the  Astraean  and  Meandrina-like 
types,  resembling  the  Reef-Builders  of  the  pres- 
ent time. 

I  have  spoken  especially  of  the  inhabitants  of  the 
Jurassic  sea  lying  between  England  and  France, 
because  it  was  there  that  were  first  found  the  re- 
mains of  some  of  the  most  remarkable  and  largest 
Jurassic  animals.  But  wherever  these  deposits 
have  been  investigated,  the  remains  contained  in 
them  reveal  the  same  organic  character,  though, 
of  course,  we  find  the  land  Reptiles  only  where 
there  happen  to  have  been  marshes,  the  aquatic 
Saurians  wherever  large  estuaries  or  bays  gave 
them  an  opportunity  of  coming  in  near  shore,  so 
that  their  bones  were  preserved  in  the  accumula- 
tions of  mud  or  clay  constantly  collecting  in  such 
localities,  —  the  Crustacea,  Shells,  or  Sea-Urchins 


THE   GEOLOGICAL  MIDDLE  AGE.  167 

on  the  old  sea-beaches,  the  Corals  in  the  neigh- 
borhood of  coral  reefs,  and  so  on.  In  short,  the 
distribution  of  animals  then  as  now  was  in  ac- 
cordance with  their  nature  and  habits,  and  we 
shall  seek  vainly  for  them  in  the  localities  where 
they  did  not  belong. 

But  when  I  say  that  the  character  of  the  Juras- 
sic animals  is  the  same,  I  mean,  that,  wherever  a 
Jurassic  sea-shore  occurs,  be  it  in  France,  Ger- 
many, England,  or  elsewhere  throughout  the 
world,  the  Shells,  Crustacea,  or  other  animals 
found  upon  it  have  a  special  character,  and  are 
not  to  be  confounded  by  any  one  thoroughly  ac- 
quainted with  these  fossils  with  the  Shells  or 
Crustacea  of  any  preceding  or  subsequent  time, 
—  that,  where  a  Jurassic  marsh  exists,  the  land 
Reptiles  inhabiting  it  are  Jurassic,  and  neither 
Triassic  nor  Cretaceous,  —  that  a  Jurassic  coral 
reef  is  built  of  Corals  belonging  as  distinctly  to 
the  Jurassic  creation  as  the  Corals  on  the  Florida 
reefs  belong  to  the  present  creation, — that,  where 
some  Jurassic  bay  or  inlet  is  disclosed  to  us  with 
the  Fishes  anciently  inhabiting  it,  they  are  as 
characteristic  of  their  time  as  are  the  Fishes  of 
Massachusetts  Bay  now. 

And  not  only  so,  but,  while  this  unity  of  crea- 
tion prevails  throughout  the  entire  epoch  as  a 
whole,  there  is  the  same  variety  of  geographical 
distribution,  the  same  circumscription  of  faunae 


168  THE   GEOLOGICAL  MIDDLE  AGE. 

within  distinct  zoological  provinces,  as  at  the 
present  time.  The  Fishes  of  Massachusetts  Bay 
are  not  the  same  as  those  of  Chesapeake  Bay,  nor 
those  of  Chesapeake  Bay  the  same  as  those  of 
Pamlico  Sound,  nor  those  of  Pamlico  Sound  the 
same  as  those  of  the  Florida  coast.  This  division 
of  the  surface  of  the  earth  into  given  areas  within 
which  certain  combinations  of  animals  and  plants 
are  confined  is  not  peculiar  to  the  present  crea- 
tion, but  has  prevailed  in  all  times,  though  with 
ever-increasing  diversity,  as  the  surface  of  the 
earth  itself  assumed  a  greater  variety  of  climatic 
conditions.  D'Orbigny  and  others  were  mistaken 
in  assuming  that  faunal  differences  have  been  in- 
troduced only  in  the  last  geological  epochs.  Be- 
sides these  adjoining  zoological  faunae,  each  epoch 
is  divided,  as  we  have  seen,  into  a  number  of 
periods,  occupying  successive  levels  one  above  an- 
other, and  differing  specifically  from  each  other 
in  time  as  zoological  provinces  differ  from  each 
other  in  space.  In  short,  every  epoch  is  to  be 
looked  upon  from  two  points  of  view :  as  a  unit, 
complete  in  itself,  having  one  character  through- 
out, and  as  a  stage  in  the  progressive  history  of 
the  world,  forming  part  of  an  organic  whole. 

As  the  Jurassic  epoch  was  ushered  in  by  the 
upheaval  of  the  Jura,  so  its  close  was  marked  by 
the  upheaval  of  that  system  of  mountains  called 


THE  GEOLOGICAL  MIDDLE  AGE.  169 

the  C6te  d'Or.  With  this  latter  upheaval  began 
the  Cretaceous  epoch,  which  we  will  examine 
with  special  reference  to  its  subdivision  into  peri- 
ods, since  the  periods  in  this  epoch  have  been 
clearly  distinguished,  and  investigated  with  espe- 
cial care.  I  have  alluded  in  the  preceding  article 
to  the  immediate  contact  of  the  Jurassic  and  Cre- 
taceous epochs  in  Switzerland,  affording  peculiar 
facilities  for  the  direct  comparison  of  their  or- 
ganic remains.  But  the  Cretaceous  deposits  are 
well  known,  not  only  in  this  inland  sea  of  ancient 
Switzerland,  but  in  a  number  of  European  basins, 
in  France,  in  the  Pyrenees,  on  the  Mediterrane- 
an shores,  and  also  in  Syria,  Egypt,  India,  and 
Southern  Africa,  as  well  as  on  our  own  continent. 
In  all  these  localities,  the  Cretaceous  remains, 
like  those  of  the  Jurassic  epoch,  have  one  organic 
character,  distinct  and  unique.  This  fact  is  espe- 
cially significant,  because  the  contact  of  their 
respective  deposits  is  in  many  localities  so  imme- 
diate and  continuous  that  it  affords  an  admirable 
test  for  the  development-theory.  If  this  is  the 
true  mode  of  origin  of  animals,  those  of  the  later 
Jurassic  beds  must  be  the  progenitors  of  those  of 
the  earlier  Cretaceous  deposits.  Let  us  see  now 
how  far  this  agrees  with  our  knowledge  of  the 
physiological  laws  of  development. 

Take  first  the  class  of  Fishes.     We  have  seen 
that  in  the  Jurassic  periods  there  were  none  of 

8 


170  THE   GEOLOGICAL   MIDDLE  AGE. 

our  common  Fishes,  none  corresponding  to  our 
Herring,  Pickerel,  Mackerel,  and  the  like,  —  no 
Fishes,  in  short,  with  thin  membranous  scales, 
but  that  the  class  was  represented  exclusively  by 
those  with  hard,  flint-like  scales.  In  the  Creta- 
ceous epoch,  however,  we  come  suddenly  upon  a 
horde  of  Fishes  corresponding  to  our  smaller 
common  Fishes  of  the  Pickerel  and  Herring 
tribes,  but  principally  of  the  kinds  found  now 
in  tropical  waters ;  there  are  none  like  our  Cods, 
Haddocks,  etc.,  such  as  are  found  at  present  in 
the  colder  seas.  The  Fishes  of  the  Jurassic  epoch 
corresponding  to  our  Sharks  and  Skates  and  Gar- 
Pikes  still  exist,  but  in  much  smaller  proportion, 
while  these  more  modern  kinds  are  very  numer- 
ous. Indeed,  a  classification  of  the  Cretaceous 
Fishes  would  correspond  very  nearly  to  one 
founded  on  those  now  living.  Shall  we,  then, 
suppose  that  the  large  reptilian  Fishes  of  the 
Jurassic  time  began  suddenly  to  lay  numerous 
broods  of  these  smaller,  more  modern,  scaly 
Fishes  ?  And  shall  we  account  for  the  diminution 
of  the  previous  forms  by  supposing  that  in  or- 
der to  give  a  fair  chance  to  the  new  kinds  they 
brought  them  forth  in  large  numbers,  while  they 
reproduced  their  own  kind  less  abundantly  ?  Ac- 
cording to  very  careful  estimates,  if  we  accept 
this  view,  the  progeny  of  the  Jurassic  Fishes 
must  have  borne  a  proportion  of  about  ninety  per 


THE   GEOLOGICAL  MIDDLE  AGE.  171 

cent  of  entirely  new  types  to  some  ten  per  cent 
of  those  resembling  the  parents.  One  would  like 
a  fact  or  two  on  which  to  rest  so  very  extraordi- 
nary a  reversal  of  all  known  physiological  laws  of 
reproduction,  but,  unhappily,  there  is  not  one. 

Still  more  unaccountable,  upon  any  theory  of 
development  according  to  ordinary  laws  of  repro- 
duction, are  those  unique,  isolated  types  limited 
to  a  single  epoch,  or  sometimes  even  to  a  single 
period.  There  are  some  very  remarkable  in- 
stances of  this  in  the  Cretaceous  deposits.  To 
make  my  statement  clearer,  I  will  say  a  word  of 
the  sequence  of  these  deposits  and  their  division 
into  periods. 

These  Cretaceous  beds  were  at  first  divided 
only  into  three  sets,  called  the  Neocomian,  or 
lower  deposits,  the  Green-Sands,  or  middle  depo- 
sits, and  the  Chalk,  or  upper  deposits.  The  Neo- 
comian, the  lower  division,  was  afterwards  sub- 
divided into  three  sets  of  beds,  called  the  Lower, 
Middle,  and  Upper  Neocomian  by  some  geolo- 
gists, the  Yalengian,  Neocomian,  and  Urgonian 
by  others.  These  three  periods  are  not  only 
traced  in  immediate  succession,  one  above  an- 
other, in  the  transverse  cut  before  described, 
across  the  mountain  of  Chaumont,  near  Neuf- 
chatel,  but  they  are  also  traced  almost  on  one 
level  along  the  plain  at  the  foot  of  the  Jura.  It 
is  evident  that  by  some  disturbance  of  the  sur- 


172  THE  GEOLOGICAL  MIDDLE  AGE. 

face  the  eastern  end  of  the  range  was  raised 
slightly,  lifting  the  lower  or  Valengian  deposits 
out  of  the  water,  so  that  they  remain  uncovered, 
and  the  next  set  of  deposits,  the  Neocomian,  is 
accumulated  along  their  base,  while  these  in  their 
turn  are  slightly  raised,  and  the  Urgonian  beds 
are  accumulated  against  them  a  little  lower 
down.  They  follow  each  other  from  east  to  west 
in  a  narrower  area,  just  as  the  Azoic,  Silurian, 
and  Devonian  deposits  follow  each  other  from 
north  to  south  in  the  northern  part  of  the  United 
States.  The  Cretaceous  deposits  have  been  inti- 
mately studied  in  various  localities  by  different 
geologists,  and  are  now  subdivided  into  at  least 
ten,  or  it  may  be  fifteen  or  sixteen  distinct  peri- 
ods, as  they  stand  at  present.  This  is,  however, 
but  the  beginning  of  the  work ;  and  the  recent 
investigations  of  the  French  geologist,  Coquand, 
indicate  that  several  of  these  periods  at  least  are 
susceptible  of  further  subdivision.  I  present  here 
a  table  enumerating  the  periods  of  the  Cretaceous 
epoch  best  known  at  present,  in  their  sequence, 
because  I  want  to  show  how  sharply  and  in  how 
arbitrary  a  manner,  if  I  may  so  express  it,  new 
forms  are  introduced.  The  names  are  simply 
derived  from  the  localities,  or  from  some  circum- 
stances connected  with  the  locality  where  each 
period  has  been  studied. 


THE   GEOLOGICAL  MIDDLE  AGE.  173 

Table  of  Periods  in  the  Cretaceous  Epoch, 

Maestrichtian •» 

Senonian \   Chalk- 

Turonian -\ 

Cenomanian j  Chalk  Marl. 

Albian -, 

APtian I  Green  Sands. 

Rhodanian ) 

Urgonian -\ 

Neocomian i-  Wealden. 

Valengian ) 

One  of  the  most  peculiar  and  distinct  of  those 
unique  types  alluded  to  above  is  that  of  the  Ru- 
distes,  a  singular  Bivalve,  in  which  the  lower 
valve  is  very  deep  and  conical,  while  the  upper 
valve  sets  into  it  as  into  a  cup.  The  subjoined 
wood-cut  represents  such  a  Bivalve.  These  Rudis- 
tes  are  found  suddenly  in  the 
Urgonian  deposits ;  there  are 
none  in  the  two  preceding  sets 
of  beds ;  they  disappear  in  the 
three  following  periods,  and 
reappear  again  in  great  num- 
bers in  the  Cenomanian,  Turo- 
nian, and  Senonian  periods, 
and  disappear  again  in  the  suc- 
ceeding one.  These  can  hardly 
be  missed  from  any  negligence  or  oversight  in  the 
examination  of  these  deposits,  for  they  are  by  no 


174  THE   GEOLOGICAL  MIDDLE  AGE. 

means  rare.  They  are  found  always  in  great 
numbers,  occupying  crowded  beds,  like  Oysters 
in  the  present  time.  So  numerous  are  they,  where 
they  occur  at  all,  that  the  deposits  containing 
them  are  called  by  many  naturalists  the  first,  sec- 
ond, third,  and  fourth  lank  of  Rudistes.  Which 
of  the  ordinary  Bivalves,  then,  gave  rise  to  this 
very  remarkable  form  in  the  class,  allowed  it  to 
die  out,  and  revived  it  again  at  various  intervals  ? 
This  is  by  no  means  the  only  instance  of  the 
same  kind.  There  are  a  number  of  types  mak- 
ing their  appearance  suddenly,  lasting  during 
one  period  or  during  a  succession  of  periods,  and 
then  disappearing  forever,  while  others,  like  the 
Eudistes,  come  in,  vanish,  and  reappear  at  a  later 
time. 

I  am  well  aware  that  the  advocates  of  the  de- 
velopment-theory do  not  state  their  views  as  I 
have  here  presented  them.  On  the  contrary,  they 
protest  against  any  idea  of  sudden,  violent,  ab- 
rupt changes,  and  maintain  that  by  slow  and  im- 
perceptible modifications  during  immense  periods 
of  time  these  new  types  have  been  introduced 
without  involving  any  infringement  of  the  ordi- 
nary processes  of  development ;  and  they  account 
for  the  entire  absence  of  corroborative  facts  in 
the  past  history  of  animals  by  what  they  call  the 
"  imperfection  of  the  geological  record."  Now, 
while  I  admit  that  our  knowledge  of  geology  is 


THE   GEOLOGICAL  MIDDLE  AGE.  175 

still  very  incomplete,  I  assert  that  just  where  the 
direct  sequence  of  geological  deposits  is  needed 
for  this  evidence,  we  have  it.  The  Jurassic  beds, 
without  a  single  modern  scaly  Fish,  are  in  imme- 
diate contact  with  the  Cretaceous  beds,  in  which 
the  Fishes  of  that  kind  are  proportionately  almost 
as  numerous  as  they  are  now ;  and  between  these 
two  sets  of  deposits  there  is  not  a  trace  of  any 
transition  or  intermediate  form  to  unite  the  rep- 
tilian Fishes  of  the  Jurassic  with  the  common 
Fishes  of  the  Cretaceous  times.  Again,  the  Cre- 
taceous beds  in  which  the  crowded  banks  of  Ru- 
distes,  so  singular  and  unique  in  form,  first  make 
their  appearance,  follow  immediately  upon  those 
in  which  all  the  Bivalves  are  of  an  entirely  differ- 
ent character.  In  short,  the  deposits  of  this  year 
along  any  sea-coast  or  at  the  mouth  of  any  of  our 
rivers  do  not  follow  more  directly  upon  those  of 
last  year  than  do  these  successive  sets  of  beds  of 
past  ages  follow  upon  each  other.  In  making 
these  statements,  I  do  not  forget  the  immense 
length  of  the  geological  periods ;  on  the  contrary, 
I  fully  accede  to  it,  and  believe  that  it  is  more 
likely  to  have  been  underrated  than  overstated. 
But  let  it  be  increased  a  thousand-fold,  the  fact 
remains,  that  these  new  types  occur  commonly  at 
the  dividing  line  where  one  period  joins  the  next, 
just  on  the  margin  of  both. 
For  years  I  have  collected  daily  among  some 


176  THE   GEOLOGICAL  MIDDLE  AGE. 

of  these  deposits,  and  I  know  the  Sea-Urchins, 
Corals,  Fishes,  Crustacea,  and  Shells  of  those  old 
shores  as  well  as  I  know  those  of  Nahant  Beach, 
and  there  is  nothing  more  striking  to  a  natural- 
ist than  the  sudden,  abrupt  changes  of  species  in 
passing  from  one  to  another.  In  the  second  set 
of  Cretaceous  beds,  the  Neocomian,  there  is  found 
a  little  Terebratula  (a  small  Bivalve  Shell)  in 
immense  quantities :  they  may  actually  be  col- 
lected by  the  bushel.  Pass  to  the  Urgonian  beds, 
resting  directly  upon  the  Neocomian,  and  there  is 
not  one  to  be  found,  and  an  entirely  new  species 
comes  in.  There  is  a  peculiar  Spatangus  (Sea- 
Urchin)  found  throughout  the  whole  series  of 
beds  in  which  this  Terebratula  occurs.  At  the 
same  moment  that  you  miss  the  Shell,  the  Sea- 
Urchin  disappears  also,  and  another  takes  its 
place.  Now,  admitting  for  a  moment  that  the 
later  can  have  grown  out  of  the  earlier  forms,  I 
maintain,  that,  if  this  be  so,  the  change  is  imme- 
diate, sudden,  without  any  gradual  transitions, 
and  is,  therefore,  wholly  inconsistent  with  all  our 
known  physiological  laws,  as  well  as  with  the 
transmutation-theory. 

There  is  a  very  singular  group  of  Ammonites 
in  the  Cretaceous  epoch,  which,  were  it  not  for 
the  suddenness  of  its  appearance,  might  seem 
rather  to  favor  the  development-theory,  from  its 
great  variety  of  closely  allied  forms.  We  have 


THE  GEOLOGICAL  MIDDLE  AGE.  177 

traced  the  Chambered  Shells  from  the  straight, 
simple  ones  of  the  earliest  epochs  up  to  the  in- 
tricate and  closely  coiled  forms  of  the  Jurassic 
epoch.  In  the  so-called  Portland  stone,  belonging 
to  the  upper  set  of  Jurassic  beds,  there  is  only 
one  type  of  Ammonite ;  but  in  the  Cretaceous 
beds,  immediately  above  it,  there  set  in  a  number 
of  different  genera  and  distinct  species,  including 
the  most  fantastic  and  seemingly  abnormal  forms. 
It  is  as  if  the  close  coil  by  which  these  shells  had 
been  characterized  during  the 
Middle  Age  had  been  sudden- 
ly broken  up  and  decomposed 
into  an  endless  variety  of  out- 
lines. Some  of  these  new  types 
still  retain  the  coil,  but  the 
whorls  are  much  less  compact 
than  before,  as  in  the  Crioceras 
(Figure  1)  ;  in  others,  the  di-  Flg' 

rection  of  the  coil  is  so  changed  as 
to  make  a  spiral,  as  in  the  Tur- 
rilites  (Figure  2) ;  or  the  shell 
starts  with  a  coil,  then  proceeds  in 
a  straight  line,  and  changes  to  a 
curve  again  at  the  other  extremity, 
as  in  the  Ancyloceras  (Figure  3), 
or  in  the  Scaphites  (Figure  4),  in 
which  the  first  coil  is  somewhat 
.  2.  closer  than  in  the  Ancyloceras  ;  or 


178 


THE   GEOLOGICAL  MIDDLE  AGE. 


the  tendency  to  a  coil  is  reduced  to  a  single 
curve,  so  as  to  give  the  shell  the  outline  of  a 


Fig.  3. 


Fig.  4. 


.  8. 


horn,  as  in  the  Toxoceras  (Figure  5)  ;  or  the 
coil  is  entirely  lost,  and  the  shell  reduced  to 
its  primitive  straight  form,  as  in  the  Baculites 

(Figure  6),  which, 
except  for  their  un- 
dulating partitions, 
might  be  mistaken 
Fig-6-  for  the  Orthocera- 

tites  of  the  Silurian  and  Devonian  epochs.  I  have 
presented  here  but  a  few  species  of  these  extra- 
ordinary Cretaceous  Ammonites,  and,  strange  to 
say,  with  this  breaking-up  of  the  type  into  a  num- 
ber of  fantastic  and  often  contorted  shapes,  it  dis- 
appears. It  is  singular  that  forms  so  unusual 
and  so  contrary  to  the  previous  regularity  of  this 
group  should  accompany  its  last  stage  of  exist- 


THE   GEOLOGICAL  MIDDLE  AGE.  179 

ence,  and  seem  to  shadow  forth  by  their  strange 
contortions  the  final  dissolution  of  their  type. 
When  I  look  upon  a  collection  of  these  old  shells, 
I  can  never  divest  myself  of  an  impression  that 
the  contortions  of  a  death-struggle  have  been 
made  the  pattern  of  living  types,  and  with  that 
the  whole  group  has  ended. 

Now  shall  we  infer  that  the  compact,  closely 
coiled  Ammonites  of  the  Jurassic  deposits,  while 
continuing  their  own  kind,  brought  forth  a  vari- 
ety of  other  kinds,  and  so  distributed  these  new 
organic  elements  as  to  produce  a  large  number 
of  distinct  genera  and  species  ?  I  confess  that 
these  ideas  are  so  contrary  to  all  I  have  learned 
from  Nature  in  the  course  of  a  long  life  that  I 
should  be  forced  to  renounce  completely  the  re- 
sults of  my  studies  in  Embryology  and  Palaeontol- 
ogy before  I  could  adopt  these  new  views  of  the 
origin  of  species.  And  while  the  distinguished 
originator  of  this  theory  is  entitled  to  our  highest 
respect  for  his  scientific  researches,  yet  it  should 
not  be  forgotten  that  the  most  conclusive  evidence 
brought  forward  by  him  and  his  adherents  is  of  a 
negative  character,  drawn  from  a  science  in  which 
they  do  not  pretend  to  have  made  personal  inves- 
tigations, that  of  Geology,  while  the  proofs  they 
offer  us  from  their  own  departments  of  science, 
those  of  Zoology  and  Botany,  are  derived  from 
observations,  still  very  incomplete,  upon  do- 


180  THE  GEOLOGICAL  MIDDLE  AGE. 

mesticated  animals  and  cultivated  plants,  which 
can  never  be  made  a  test  of  the  origin  of  wild 
species.* 

In  my  next  article  I  shall  show  the  relation  be- 
tween the  Cretaceous  and  Tertiary  epochs,  and 
see  whether  there  is  any  reason  to  believe  that 
the  gigantic  Mammalia  of  more  modern  times 
were  derived  from  the  Reptiles  of  the  Secondary 
age. 

*  The  advocates  of  the  development-theory  allude  to  the  meta- 
morphosis of  animals  and  plants  as  supporting  their  view  of  a 
change  of  one  species  into  another.  They  compare  the  passage 
of  a  common  leaf  into  the  calyx  or  crown-leaves  in  plants,  or 
that  of  a  larva  into  a  perfect  insect,  to  the  passage  of  one  spe- 
cies into  another.  The  only  objection  to  this  argument  seems 
to  be,  that,  whereas  Nature  daily  presents  us  myriads  of  ex- 
amples of  the  one  set  of  phenomena,  showing  it  to  be  a  norm, 
not  a  single  instance  of  the  other  has  ever  been  known  to  occur 
either  in  the  animal  or  in  the  vegetable  kingdom. 


VII. 

THE    TERTIARY    AGE,   AND    ITS    CHAR- 
ACTERISTIC ANIMALS. 

IN  entering  upon  the  Tertiaries,  we  reach  that 
geological  age  which,  next  to  his  own,  has 
the  deepest  interest  for  man.  The  more  striking 
scenes  of  animal  life,  hitherto  confined  chiefly  to 
the  ocean,  are  now  on  land ;  the  extensive  sheets 
of  fresh  water  are  filled  with  fishes  of  a  compar- 
atively modern  character, — with  Whitefish,  Pick- 
erel, Perch,  Eels,  etc.,  —  while  the  larger  quad- 
rupeds are  introduced  upon  the  continents  so 
gradually  prepared  to  receive  them.  The  con- 
nection of  events  throughout  the  Tertiaries,  con- 
sidered as  leading  up  to  the  coming  of  man,  may 
be  traced  not  only  in  the  physical  condition  of  the 
earth,  and  in  the  presence  of  the  large  terrestrial 
Mammalia,  but  also  in  the  appearance  of  those 
groups  of  animals  and  plants  which  we  naturally 
associate  with  the  domestic  and  social  existence 
of  man.  Cattle  and  Horses  are  first  found  in  the 
middle  Tertiaries ;  the  grains,  the  Rosaceae,  with 
their  variety  of  fruits,  the  tropical  fruit-trees, 


182  THE  TERTIARY  AGE,  AND 

Oranges,  Bananas,  etc.,  the  shade-  and  cluster- 
trees,  so  important  to  the  comfort  and  shelter  of 
man,  are  added  to  the  vegetable  world  during 
these  epochs.  The  fossil  vegetation  of  the  Terti- 
aries  is,  indeed,  most  interesting  from  this  point 
of  view,  showing  the  gradual  maturing  and  com- 
pletion of  those  conditions  most  intimately  associ- 
ated with  human  life.  The  earth  had  already  its 
seasons,  its  spring  and  summer,  its  autumn  and 
winter,  its  seed-time  and  harvest,  though  neither 
sower  nor  reaper  was  there ;  the  forests  then,  as 
now,  dropped  their  thick  carpet  of  leaves  upon 
the  ground  in  the  autumn,  and  in  many  localities 
they  remain  where  they  originally  fell,  with  a 
layer  of  soil  between  the  successive  layers  of 
leaves,  —  a  leafy  chronology,  as  it  were,  by  which 
we  read  the  passage  of  the  years  which  divided 
these  deposits  from  each  other.  Where  the  leaves 
have  fallen  singly  on  a  clayey  soil  favorable  for 
receiving  such  impressions,  they  have  daguerro- 
typed  themselves  with  the  most  wonderful  accu- 
racy, and  the  Oaks,  Poplars,  Willows,  Maples, 
Walnuts,  Gum-  and  Cinnamon-trees,  etc.,  of  the 
Tertiaries  are  as  well  known  to  us  as  are  those  of 
our  own  time. 

It  was  an  eventful  day,  not  only  for  science, 
but  for  the  world,  when  a  Siberian  fisherman 
chanced  to  observe  a  singular  mound  lying  near 
the  mouth  of  the  River  Lena,  where  it  empties 


ITS  CHARACTERISTIC  ANIMALS.  183 

into  the  Arctic  Ocean.  During  the  warmer  sum- 
mer-weather, he  noticed,  that,  as  the  snow  gradu- 
ally melted,  this  mound  assumed  a  more  distinct 
and  prominent  outline,  and  at  length,  on  one  side 
of  it,  where  the  heat  of  the  sun  was  greatest,  a 
dark  body  became  exposed,  which,  when  com- 
pletely uncovered,  proved  to  be  that  of  an  im- 
mense elephant,  in  so  perfect  a  state  of  preserva- 
tion that  the  dogs  and  wolves  were  attracted  to  it 
as  by  the  smell  of  fresh  meat,  and  came  to  feed 
upon  it  at  night.  The  man  knew  little  of  the 
value  of  his  discovery,  but  the  story  went  abroad, 
and  an  Englishman  travelling  in  Russia,  being 
curious  to  verify  it,  visited  the  spot,  and  actually 
found  the  remains  where  they  had  been  reported 
to  lie,  on  the  frozen  shore  of  the  Arctic  Sea, — 
strange  burial-place  enough  for  an  animal  never 
known  to  exist  out  of  tropical  climates.  Little 
beside  the  skeleton  was  left,  though  parts  of  the 
skin  remained  covered  with  hair,  showing  how 
perfect  must  have  been  the  condition  of  the  body 
when  first  exposed.  The  tusks  had  been  sold  by 
the  fisherman ;  but  Mr.  Adams  succeeded  in  re- 
covering them ;  and  collecting  all  the  bones,  ex- 
cept those  of  one  foot,  which  had  been  carried  off 
by  the  wolves,  he  had  them  removed  to  St.  Pe- 
tersburg, where  the  skeleton  now  stands  in  the 
Imperial  Museum.  The  inhabitants  of  Siberia 
seem  to  be  familiar  with  this  animal,  which  they 


184  THE  TERTIARY  AGE,  AND 

designate  by  the  name  of  Mammoth^  while  natu- 
ralists call  it  Elephas  primigenius.  The  circum- 
stance that  they  abound  in  the  frozen  drift  of  the 
great  northern  plain  of  Asia,  and  are  occasionally 
exposed  in  consequence  of  the  wearing  of  the 
large  rivers  traversing  Siberia,  has  led  to  the  su- 
perstition among  the  Tongouses,  that  the  Mam- 
moths live  under  ground,  and  die  whenever,  on 
coming  to  the  surface,  the  sunlight  falls  upon 
them. 


Mammoth,  the  Elephns  primigenius. 

Had  this  been  the  only  creature  of  the  kind 
found  so  far  from  the  countries  to  which  ele- 
phants are  now  exclusively  confined,  it  might 
have  been  believed  that  some  strange  accident 
had  brought  it  to  the  spot  where  it  was  buried. 
But  it  was  not  long  before  similar  remains  were 


ITS  CHARACTERISTIC  ANIMALS.  185 

found  in  various  parts  of  Europe,  —  in  Russia,  in 
Germany,  in  Spain,  and  in  Italy.  The  latter 
were  readily  accounted  for  by  the  theory  that 
they  must  be  the  remains  of  the  Carthaginian 
elephants  brought  over  by  the  armies  of  Hanni- 
bal, while  it  was  suggested  that  the  others  might 
have  been  swept  from  India  by  some  great  flood, 
and  stranded  where  they  were  found.  It  was 
Cuvier,  entitled  by  his  intimate  acquaintance 
with  the  anatomy  of  living  animals  to  an  authori- 
tative opinion  in  such  matters,  who  first  dared  to 
assert  that  these  remains  belonged  to  no  elephant 
of  our  period.  He  rested  this  belief  upon  struct- 
ural evidence,  and  insisted  that  an  Indian  ele- 
phant, brought  upon  the  waves  of  a  flood  to  Si- 
beria, would  be  an  Indian  elephant  still,  while  all 
these  remains  differed  in  structure  from  any  spe- 
cies existing  at  present.  This  statement  aroused 
research  in  every  direction,  and  the  number  of 
fossil  Mammalia  found  within  the  next  few  years, 
and  proved  by  comparison  to  be  different  from 
any  living  species,  soon  demonstrated  the  truth 
of  his  conclusion. 

Shortly  after  the  discovery  of  fossil  elephants 
had  opened  this  new  path  of  investigation,  some 
curious  bones  were  found  by  some  workmen  in 
the  quarries  of  Montmartre,  near  Paris,  and 
brought  to  Cuvier  for  examination.  Although 
few  in  numbers,  and  affording  but  very  scanty 


186  THE  TERTIARY  AGE,  AND 

data  for  such  a  decision,  he  at  once  pronounced 
them  to  be  the  remains  of  some  extinct  animal 
preceding  the  present  geological  age.  Here, 
then,  at  his  very  door,  as  it  were,  was  a  settle- 
ment of  that  old  creation  in  which  he  could  pur- 
sue the  inquiry,  already  become  so  important  in 
its  bearings.  It  was  not  long  before  other  bones 
of  the  same  kind  were  found,  though  nothing  as 
yet  approaching  an  entire  skeleton.  However, 
with  such  means  as  he  had,  Cuvier  began  a  com- 
parison with  all  the  living  Mammalia,  —  with  the 
human  skeleton  first,  with  Monkeys,  with  the 
larger  Carnivora  and  Ruminants,  then  with  all 
the  smaller  Mammalia,  then  with  the  Pachy- 
derms ;  and  here,  for  the  first  tune,  he  began  to 
find  some  resemblance.  He  satisfied  himself  that 
the  animal  must  have  belonged  to  the  family  of 
Pachyderms ;  and  he  then  proceeded  to  analyze 
and  compare  all  the  living  species,  till  he  had  col- 
lected ample  evidence  to  show  that  the  bones  in 
question  did  not  correspond  with  any  species,  and 
could  not  even  be  referred  to  any  genus,  now  in 
existence.  At  length  there  was  discovered  at 
Montmartre  an  upper  jaw  of  the  same  animal,  — 
next  a  lower  jaw,  matching  the  upper  one,  and 
presently  a  whole  head  with  a  few  backbones 
was  brought  to  light.  These  were  enough,  with 
Cuvier's  vast  knowledge  of  animal  structure,  to 
give  him  a  key  to  the  whole  skeleton.  At  about 


ITS   CHARACTERISTIC  ANIMALS.  187 

the  same  time,  in  the  same  locality,  were  found 
other  bones  and  teeth  also,  differing  from  those 
first  discovered,  and  yet  equally  unlike  those  of 
any  living  animal.  The  first  evidently  belong- 
ing to  some  stout  and  heavy  animal,  the  others 
were  more  slender  and  of  lighter  build.  From 
these  fragments,  ample  evidence  to  him  of  his 
results,  he  drew  the  outlines  of  two  animals : 
one  which  he  called  the  Palaeotherium  (old 


Paloeotheriura. 

animal),  a  figure  of  which  is  given  in  the  above 
wood-cut,  and  the  other  Anoplotherium  (animal 
without  fangs).  He  presented  these  figures  with 
an  explanatory  memoir  at  the  Academy,  and  an- 
nounced them  as  belonging  to  some  creation  pre- 
ceding the  present,  since  no  such  animals  had 
ever  existed  in  our  own  geological  period.  Such 
a  statement  was  a  revelation  to  the  scientific 
world :  some  looked  upon  it  with  suspicion  and 
distrust ;  others,  who  knew  more  of  comparative 
anatomy,  hailed  it  as  introducing  a  new  era  in 


188  THE  TERTIARY  AGE,  AND 

science ;  but  it  was  not  till  complete  specimens 
were  actually  found  of  animals  corresponding  per- 
fectly to  those  figured  and  described  by  Cuvier, 
and  proving  beyond  a  doubt  their  actual  exist- 
ence in  ancient  times,  that  all  united  in  wonder 
and  admiration  at  the  result  obtained  by  him 
with  such  scanty  means. 

It  would  seem  that  the  family  of  Pachyderm 
was  largely  represented  among  the  early  Mam- 
malia ;  for,  since  Cuvier  named  these  species,  a 
number  of  closely  allied  forms  have  been  found 
in  deposits  belonging  to  the  same  epoch.  Of 
course,  the  complete  specimens  are  rare ;  but  the 
fragments  of  such  skeletons  occur  in  abundance, 
showing  that  these  old-world  Pachyderms,  re- 
sembling the  Tapirs  more  than  any  other  living 
representatives  of  the  family,  were  very  numerous 
in  the  lower  Tertiaries. 

There  is,  however,  one  animal  now  in  exist- 
ence, forming  one  of  those  singular  links  before 
alluded  to  between  the  present  and  the  past,  of 
which  I  will  say  a  few  words  here,  though  its  re- 
lation is  rather  with  a  later  group  of  Tertiary 
Pachyderms  than  with  those  described  by  Cuvier. 
On  the  coast  of  Florida  there  is  an  animal  of  very 
massive,  clumsy  build,  long  considered  to  be  a 
Cetacean,  but  now  recognized,  by  some  natural- 
ists at  least,  as  belonging  to  the  order  of  Pach- 
yderms. In  form  it  resembles  the  Cetaceans, 


ITS   CHAEACTEEISTIC  ANIMALS.  189 

though  it  has  a  fan-shaped  tail,  instead  of  the 
broad  flapper  of  the  Whales.  It  inhabits  fresh 
waters  or  shoal  waters,  and  is  not  so  exclusively 
aquatic  as  the  oceanic  Cetaceans.  Its  most  strik- 
ing feature  is  the  form  of  the  lower  jaw,  which  is 
bent  downward,  with  the  front  teeth  hanging 
from  it.  This  animal  is  called  the  Manatee,  or 
Sea-Cow.  There  are  three  species  known  to 
naturalists,  —  one  in  Tampa  Bay,  one  in  the 
Amazon,  and  one  in  the  Red  Sea.  In  the  Ter- 
tiary deposits  of  Germany  there  has  been  found 
an  animal  allied  in  some  of  its  features  to  those 
described  by  Cuvier,  but  it  has  the  crown  of  its 
teeth  folded  like  the  Tapir,  while  the  lower  jaw 
is  turned  down  with  a  long  tusk  growing  from  it. 
This  animal  has  been  called  the  Dinotherium.  A 
part  of  the  head,  showing  the  heavy  jaws  and  the 
formidable  tusk,  is 
represented  in  the 
subjoined  wood-cut. 
Its  hanging  lower 
jaw,  with  the  pro- 
truding tusk,  corre- 
sponds perfectly  to 
the  formation  of  the 
lower  jaw  and  teeth 
in  the  Manatee. 
Some  resemblance 
of  the  Dinotherium  to  the  Mastodon  suggested  a 


190  THE  TERTIARY  AGE,  AND 

comparison  with  that  animal  as  the  next  step  in 
the  investigation,  when  it  was  found  that  at  the 
edge  of  the  lower  jaw  of  the  latter  there  was  a 
pit  with  a  small  projecting  tooth,  also  correspond- 
ing exactly  in  its  position  to  the  tusk  in  the  Di- 
notherium.  The  Elephant  was  now  examined; 
and  in  him  also  a  rudimentary  tooth  appeared  in 
the  lower  jaw,  not  cut  through,  but  placed  in  the 
same  relation  to  the  jaw  and  the  other  teeth  as 
that  of  the  Mastodon.  It  would  seem,  then,  that 
the  Manatee  makes  one  in  this  series  of  Dinothe- 
rium,  Mastodon,  and  Elephant,  and  represents 
the  aquatic  Pachyderms,  occupying  the  same  re- 
lation to  the  terrestrial  Pachyderms  as  the  Seals 
bear  to  the  terrestrial  Carnivora,  and,  like  them, 
lowest  in  structure  among  their  kind. 

The  announcement  of  Cuvier's  results  stimu 
lated  research,  and  from  this  time  forward  Ter- 
tiary Mammalia  became  the  subject  of  extensive 
and  most  important  investigations  among  natu- 
ralists. The  attention  of  collectors  once  drawn 
to  these  remains,  they  were  found  in  such  num- 
bers that  the  wonder  was  how  they  had  been  so 
long  hidden  from  the  observation  of  men.  They 
remind  us  chiefly  of  tropical  animals ;  indeed. 
Tigers,  Hyenas,  Rhinoceroses,  Hippopotamuses, 
Mastodons,  and  Elephants  had  their  home  in 
countries  which  now  belong  to  the  Cold  Temper- 
ate Zone,  showing  that  the  climate  in  these  lati 


ITS  CHARACTERISTIC  ANIMALS.  191 

tudes  was  much  milder  then  than  it  is  at  present. 
Bones  of  many  of  these  animals  were  found  in 
caverns  in  Germany,  France,  Italy,  and  England. 
Perhaps  the  story  of  Kirkdale  Cave,  where  the 
first  important  discovery  of  this  kind  was  made 
on  English  soil,  may  not  be  so  well  known  to 
American  readers  as  to  forbid  its  repetition  here. 
It  was  in  the  summer  of  1821  that  some  work- 
men, employed  in  quarrying  stone  upon  the  slope 
of  a  limestone  hill  at  Kirkdale,  in  Yorkshire,  came 
accidentally  upon  the  mouth  of  a  cavern.  Over- 
grown with  grass  and  bushes,  the  mouth  of  this 
cave  in  the  hill-side  had  been  effectually  closed 
against  all  intruders,  and  it  was  strange  that  its 
existence  had  never  been  suspected.  The  hole 
was  small,  but  large  enough  to  admit  a  man  on 
his  hands  and  knees ;  and  the  workmen,  creep- 
ing in  through  the  opening,  found  that  it  led  into 
a  cavern,  broad  in  some  parts,  but  low  through- 
out. There  were  only  a  few  spots  where  a  man 
could  stand  upright ;  but  it  was  quite  extensive, 
with  branches  opening  out  from  it,  some  of  which 
have  not  yet  been  explored.  The  whole  floor  was 
strewn,  from  one  end  to  the  other,  with  hundreds 
of  bones,  like  a  huge  dog-kennel.  The  workmen 
wondered  a  little  at  their  discovery,  but,  remem- 
bering that  there  had  been  a  murrain  among  the 
cattle  in  this  region  some  years  before,  they  came 
to  the  conclusion  that  these  must  be  the  bones  of 


192  THE  TERTIARY  AGE,  AND 

cattle  that  had  died  in  great  numbers  at  that 
time ;  and,  having  so  settled  the  matter  to  their 
own  satisfaction,  they  took  little  heed  to  the 
bones,  but  threw  many  of  them  out  on  the  road 
with  the  common  limestone.  Fortunately,  a  gen- 
tleman, living  in  the  neighborhood,  whose  atten- 
tion had  been  attracted  to  them,  preserved  them 
from  destruction;  and  a  few  months  after  the 
discovery  of  the  cave,  Dr.  Buckland,  the  great 
English  geologist,  visited  Kirkdale,  to  examine 
its  strange  contents,  which  proved  indeed  stran- 
ger than  any  one  had  imagined;  for  many  of 
these  remains  belonged  to  animals  never  before 
found  in  England.  The  bones  of  Hyenas,  Tigers, 
Elephants,  Rhinoceroses,  and  Hippopotamuses 
were  mingled  with  those  of  Deer,  Bears,  Wolves, 
Foxes,  and  many  smaller  creatures.  The  bones 
were  gnawed,  and  many  were  broken,  evidently 
not  by  natural  decay,  but  seemed  to  have  been 
snapped  violently  apart.  After  the  most  complete 
investigation  of  the  circumstances,  Dr.  Buckland 
convinced  himself,  and  proved  to  the  satisfaction 
of  all  scientific  men,  that  the  cave  had  been  a 
den  of  Hyenas  *  at  a  time  when  they,  as  well  as 

*  Among  the  other  facts  showing  that  Kirkdale  Cave  had 
been  the  den  of  these  animals,  and  not  tenanted  as  their  home 
by  any  of  the  other  creatures  whose  remains  occurred  there,  were 
the  excrements  of  the  Hyenas  found  in  considerable  quantity  by 
Dr.  Buckland,  and  identified  as  such  by  the  keeper  of  a  menage- 


ITS   CHARACTERISTIC  ANIMALS.  193 

Tigers,  Elephants,  Rhinoceroses,  etc.,  existed  in 
England  in  as  great  numbers  as  they  now  do  in 
the  wildest  parts  of  tropical  Asia  or  Africa.  The 
narrow  entrance  to  the  cave  still  retains  the  marks 
of  grease  and  hair,  such  as  one  may  see  on  the 
bars  of  a  cage  in  a  menagerie  against  which  the 
imprisoned  animals  have  been  in  the  habit  of 
rubbing  themselves  constantly,  and  there  were 
marks  of  the  same  kind  on  the  floor  and  walls. 
It  was  evident  that  the  Hyenas  were  the  lords  of 
this  ancient  cavern,  and  the  other  animals  their 
unwilling  guests ;  for  the  remains  of  the  latter 
were  those  which  had  been  most  gnawed,  broken, 
and  mangled ;  and  the  head  of  an  enormous  Hy- 
ena, with  gigantic  fangs  found  complete,  bore 
ample  evidence  to  their  great  size  and  power. 
Some  of  the  animals,  such  as  the  Elephants,  Rhi- 
noceroses, etc.,  could  not  have  been  brought  into 
the  cave  without  being  first  killed  and  torn  to 
pieces,  for  it  is  not  large  enough  to  admit  them. 
But  their  gnawed  and  broken  bones  attest,  never- 
theless, that  they  were  devoured  like  the  rest; 
and  probably  the  Hyenas  then  had  the  same  pro- 
pensity which  characterizes  those  of  our  own 

rie.  Any  one  who  may  wish  to  read  the  whole  history  of  Dr. 
Buckland's  investigations  of  this  matter,  showing  the  patience 
and  sagacity  with  which  he  collected  and  arranged  the  evidence, 
will  find  a  full  account  of  Kirkdale  Cave  and  other  caverns  con- 
taining fossil  bones  -in  his  "  Keliquse  Diluvianse." 

9  M 


194  THE  TERTIARY  AGE,  AND 

time,  to  tear  in  pieces  the  body  of  any  dead  ani- 
mal, and  carry  it  to  their  den  to  feed  upon  it 
apart. 

While  Kirkdale  Cave  was  evidently  the  haunt 
of  Hyenas  chiefly,  other  caverns  in  Germany  and 
France  were-  tenanted  in  a  similar  manner  by  a 


gigantic  species  of  Bear.  Their  remains,  mingled 
with  those  of  the  animals  on  which  they  fed,  have 
been  found  in  great  numbers  in  the  Cavern  of 
Gailenreuth)  in  Franconia.  The  subjoined  wood- 
cut shows  the  head  of  this  formidable  beast,  which 
must  have  exceeded  in  size  any  Bear  now  living. 
Indeed,  although  there  were  many  smaller  kinds, 
and  the  other  types  of  the  Animal  Kingdom  in 
the  Tertiaries  seem  to  approach  very  nearly  both 
in  size  and  general  character  their  modern  repre- 


ITS  CHAEACTEEISTIC  AND1ALS.  195 

sentatives,  yet,  on  the  whole,  the  earlier  Mamma 
lia  were  giants  in  comparison  with  those  now  liv- 
ing. The  Mastodon  and  Mammoth,  as  compared 
with  the  modern  Elephant,  the  Megatherium,  as 
compared  with  the  Sloths,  or  Ant-Eaters  of  pres- 
ent times,  the  Hyenas  and  Bears  of  the  European 
caverns,  and  the  fossil  Elk  of  Ireland,  by  the  side 


of  which  even  the  Moose  of  our  Northern  woods 
is  belittled,  are  remarkable  instances  in  proof  of 
this.  One  cannot  but  be  struck  with  the  fact 
that  this  first  representation  of  Mammalia,  the 
very  impersonation  of  brute  force  in  power,  size, 
and  ferocity,  immediately  preceded  the  introduc- 
tion of  man,  with  whose  creation  intelligence  and 


196  THE  TERTIARY  AGE,  AND 

moral  strength  became  the  dominant  influences 
on  earth. 

Among  these  huge  Tertiary  Mammalia,  one  of 
those  most  common"  on  the  North- American  con- 
tinent seems  to  have  been  the  Mastodon.  The 
magnificent  specimens  preserved  in  this  country 
are  too  well  known  to  require  description.  The 
remains  of  the  Rhinoceros  occur  also  in  the  re- 
cent Tertiary  deposits  of  North  America,  though 
as  yet  no  perfect  skeletons  have  been  found.  The 
Edentata,  now  confined  to  South  America  and  the 
western  coast  of  Africa,  were  also  numerous  in  the 
Southern  States  during  that  time ;  their  remains 
have  been  found  as  far  north  as  the  Salt  Lick  in 
Kentucky.  But  we  must  not  judge  of  the  Ter- 
tiary Edentata  by  any  now  known  to  us.  The 
Sloths,  the  Armadillos,  the  Ant-Eaters,  the  Pan- 
golins, are  all  animals  of 
rather  small  size ;  but  for- 
merly they  were  repre- 
sented by  the  gigantic 
Megatherium,  the  Mega- 
lonyx,  and  the  Mylodon, 
some  of  which  were  lar- 
ger than  the  Elephant, 
and  others  about  the  size 
of  the  Rhinoceros  or  Hip- 
popotamus. The  Sub-  Mylodon. 
joined  wood-cut  represents  a  Mylodon  in  the  act 


ITS   CHAEACTERISTIC  ANIMALS.  197 

of  lifting  himself  against  the  trunk  of  a  tree. 
They  were  clumsy  brutes,  and  though  their  limbs 
were  evidently  built  with  reference  to  powerful 
movements,  perhaps  climbing,  or  at  least  rising 
on  their  hind  quarters,  the  act  of  climbing  with 
them  cannot  have  had  anything  of  the  nimbleness 
or  activity  generally  associated  with  it.  On  the 
contrary,  they  probably  were  barely  able  to  sup- 
port their  huge  bodies  on  the  hind  limbs,  which 
are  exceedingly  massive,  and  on  the  stiff,  heavy 
tail,  while  they  dragged  down  with  their  front 
limbs  the  branches  of  the  trees,  and  fed  upon 
them  at  leisure.  The  Zoological  Museum  at 
Cambridge  is  indebted  to  the  generosity  of  Mr. 
Joshua  Bates  for  a  very  fine  set  of  casts  taken 
from  the  Megatherium  bones  preserved  in  the 
British  Museum  and  the  College  of  Surgeons. 
They  are  now  mounted,  and  may  be  seen  in  one 
of  the  exhibition-rooms  of  the  building.  Large 
Reptiles,  but  very  unlike  those  of  the  Creta- 
ceous and  Jurassic  epochs,  belonging  chiefly  to 
the  types  of  Turtles,  Crocodiles,  ^Pythons,  and 
Salamanders,  existed  during  the  Tertiary  epochs. 
The  subjoined  wood-cut  represents  a  gigantic  Sal- 
amander of  the  Tertiary  deposits.  It  is  a  curious 
fact,  illustrative  of  the  ignorance  of  all  anatomi- 
cal science  in  those  days,  that,  when  the  remains 
of  this  reptile  (Andrias,  as  it  is  now  called)  were 
first  discovered  towards  the  close  of  the  seven- 


198  THE   TERTIARY  AGE,   AND 

teenth  century,  they  were  described  by  old  Profes- 
sor Scheuchzer  as  the  bones  of  an  infant  destroyed 


Andrias. 

by  the  Deluge,  and  were  actually  preserved,  not 
for  their  scientific  value,  but  as  precious  relics  of 
the  Flood,  and  described  in  a  separate  pamphlet, 
entitled,  "  Homo  Diluvii  Testis."  Among  the 
Tertiary  Reptiles  the  Turtles  seem  to  have  been 
a  very  prominent  type,  by  their  size  as  well  as  by 
their  extensive  distribution.  Their  remains  have 
been  found  both  in  the  far  West  and  in  the  East. 
The  fossil  Turtles  of  Nebraska  are  well  known  to 
American  naturalists ;  but  the  Oriental  one  ex- 
ceeds them  in  size,  and  is,  indeed,  the  most  gi- 
gantic representative  of  the  order  known  thus 
far.  A  man  could  stand  under  the  arch  of  the 
shield  of  the  old  Himalayan  Turtle  preserved  in 
the  British  Museum. 


ITS   CHARACTEKISTIC  ANIMALS.  199 

It  would  carry  me  too  far,  were  I  to  attempt 
to  give  anything  more  than  the  most  cursory 
sketch  of  the  animals  of  the  Tertiary  age ;  and, 


indeed,  they  are  so  well  known,  and  have  been 
so  fully  represented  in  text-books,  that  I  fear 
some  of  my  readers  may  think  even  now  that  I 
have  dwelt  too  long  upon  them.  Monkeys  were 
unquestionably  introduced  upon  earth  before  the 
close  of  the  Tertiaries ;  some  bones  have  been 
found  in  Southern  France,  and  also  on  Mount 
Pentelicus  in  Greece,  in  the  later  Tertiary  depos- 
its ;  but  these  remains  have  not  yet  been  collected 
in  sufficient  number  to  establish  much  more  than 
the  fact  of  their  presence  in  the  animal  creation 


200  THE  TERTIARY  AGE,  AND 

at  that  time.  I  do  not  offer  any  opinion  respect- 
ing the  fossil  human  bones  so  much  discussed 
recently,  because  the  evidence  is  at  present  too 
scanty  to  admit  of  any  decisive  judgment  con- 
cerning them.  It  becomes,  however,  daily  more 
probable  that  facts  will  force  us  sooner  or  later  to 
admit  that  the  creation  of  man  lies  far  beyond 
any  period  yet  assigned  to  it,  and  that  a  succes- 
sion of  human  races,  as  of  animals,  have  followed 
one  another  upon  the  earth.  It  may  be  the  in- 
estimable privilege  of  our  young  naturalists  to 
solve  this  great  problem,  but  the  older  men  of 
our  generation  must  be  content  to  renounce  this 
hope ;  we  may  have  some  prophetic  vision  of  its 
fulfilment,  we  may  look  from  afar  into  the  land 
of  promise,  but  we  shall  not  enter  in  and  pos- 
sess it. 

The  other  great  types  of  the  Animal  Kingdom 
are  very  fully  represented  in  the  Tertiaries,  and 
in  their  general  appearance  they  approach  much 
more  closely  those  of  the  present  creation  than 
of  any  previous  epochs.  Professor  Heer  has  col- 
lected and  described  the  Tertiary  Insects  in  great 
number  and  variety ;  and  the  Butterflies,  Bugs, 
Flies,  Grasshoppers,  Dragon-Flies,  Beetles,  etc., 
described  in  his  volumes,  would  hardly  be  distin- 
guished from  our  own,  except  by  a  practised  en- 
tomologist. Among  Crustacea,  the  Shrimp-like 
forms  of  the  earlier  geological  epochs  have  be- 


ITS   CHAEACTERISTIC  ANIMALS.  201 

come  much  less  conspicuous,  while  Crabs  and 
Lobsters  are  now  the  prominent  representatives 
of  the  class.  Among  Mollusks,  the  Chambered 
Shells,  hitherto  so  numerous,  have  become,  as 
they  now  are,  very  few  in  comparison  with  the 
naked  Cephalopods.  The  Nautili,  however,  re- 
semble those  now  living  in  the  Pacific  Ocean ; 
and  some  fragments  of  the  Paper-Nautilus  have 
been  found,  showing  that  this  delicate  shell  was 
already  in  existence.  There  is  one  very  peculiar 
type  of  this  class,  belonging  to  the  Tertiaries, 
which  should  not  be  passed  by  unnoticed.  It 
partakes  of  the  character  both  of  the  Cretaceous 
Belemnites  and  of  the  living  Cuttle-Fish,  and  is 
known  as  the  Spirulirostra.  Another  very  char- 


Spirnlirostra. 

acteristic  group  among  the  Tertiary  Shells  is  that 
of  the  Nummulites,  formerly  placed  by  natural- 
ists in  immediate  proximity  with  the  Ammonites, 
on  account  of  their  internal  partitions.  This  is 
now  admitted  to  have  been  an  error ;  their  posi- 
tion is  not  yet  fully  determined,  but  they  cer- 
tainly stand  very  low  in  the  scale,  and  have  no 

9* 


202 


THE  TERTIAEY  AGE,   AND 


Numraulite. 


affinity  whatever  with  the  Cephalopods.  The  sub- 
joined wood-cut  represents 
one  of  these  Shells,  so  nu- 
merous in  the  Tertiaries 
that  large  masses  of  rock 
consist  of  their  remains. 
The  Univalve  Shells  or  Gas- 
teropods  of  the  Tertiaries 
embraced  all  the  families 
now  living,  including  land 

and  fresh-water  Shells  as  well 

as  the  marine  representatives 

of  the  type.     Some  of  the  lat- 

ter,  as,  for  instance,  the  Ce- 

rithium,  are  accumulated  in 

vast  numbers.    The  limestone 

quarries  out  of  which  Paris  is 

chiefly    built    consist    almost 

wholly  of  these  Shells.     The 

fresh-water  basins  were  filled 

with  Helices,  one  of  which  is 

represented  in   the  following  Cerithium. 

wood-cut,  with  Planorbis, 
Limnaeus,  and  other  Shells 
resembling  those  now  so 
common  in  all  our  lakes 
and  rivers,  and  differing 
from  the  living  ones  only 
by  slight  specific  characters. 


Helix. 


ITS  CHARACTERISTIC  ANIMALS.  203 

The  Bivalves  also  have  the  same  resemblance 
to  the  present  ones,  including  fresh-water  Mus- 
sels, as  the  marine  Clams  and  Oysters.  Among 
Radiates,  the  higher  Echini  (Sea-Urchins)  have 
become  numerous,  while  the  other  Echinoderms 
of  all  families  abound.  Corals  include,  for  the 
first  time,  the  more  highly  organized  Madrepores. 

In  the  Tertiaries  we  see  the  dawn  of  the  pres- 
ent condition  of  things,  not  only  in  the  character 
of  the  animals  anci  plants,  but  in  the  height  of 
the  mountains  and  in  the  distribution  of  land  and 
sea. 

Let  us  give  a  glance  at  the  continents  whose 
growth  we  have  been  following,  and  see  what 
these  more  recent  geological  epochs  have  done 
for  their  completion.  In  Europe  they  have  filled 
'the  basin  in  Central  France,  and  converted  all 
that  region  into  dry  land;  they  have  filled  also 
the  channel  between  France  and  Spain ;  they 
have  united  Central  Russia  with  the  rest  of  Eu- 
rope by  the  completion  of  Poland,  and  have 
greatly  enlarged  Austria  and  Turkey  ;  they  have 
completed  the  promontories  of  Italy  and  Greece, 
and  have  converted  the  inland  sea  at  the  foot  of 
the  Jura  into  the  plain  of  Switzerland.  But  this 
fruitful  period  in  the  progress  of  the  world,  when 
the  character  of  organic  life  was  higher  and  the 
physical  features  of  the  earth  more  varied  than 
ever  before,  was  not  without  its  storms  and 


204  THE  TERTIARY  AGE,   AND 

convulsions.  The  Pyrenees,  the  Apennines,  the 
Alps,  and  with  them  the  whole  range  of  the  Cau- 
casus and  Himalayas,  were  raised  either  immedi- 
ately after  the  Cretaceous  epoch,  or  in,  the  course 
of  the  Tertiaries.  Indeed,  with  this  most  signifi- 
cant passage  in  her  history,  Europe  acquired  all 
her  essential  characters.  There  remained,  it  is 
true,  much  to  be  done  in  what  is  called  by  geolo- 
gists "  modern  times."  The  work  of  the  artist  is 
not  yet  finished  when  his  statue  is  blocked  out 
and  the  grand  outline  of  his  conception  stands 
complete ;  and  there  still  remained,  after  the 
earth  was  rescued  from  the  water,  after  her 
framework  of  mountains  was  erected,  after  her 
soil  was  clothed  with  field  and  forest,  processes 
by  which  her  valleys  were  to  be  made  more  fruit- 
ful, her  gulfs  to  be  filled  with  the  rich  detritus 
poured  into  them  by  the  rivers,  her  whole  surface 
to  be  rendered  more  habitable  for  the  higher 
races  who  were  to  possess  it. 

We  left  America  at  the  close  of  the  Carbonifer- 
ous epoch.  A  glance  at  the  geological  map  will 
show  the  reader  that  during  the  Permian,  Trias- 
sic,  and  Jurassic  epochs  little  was  added  to  the 
United  States,  though  here  and  there  deposits  be- 
longing to  each  of  them  crop  out.  In  the  Creta- 
ceous epoch,  however,  large  tracts  of  land  were 
accumulated,  chiefly  in  the  South  and  West ;  and 
during  the  Tertiaries  the  continent  was  very 


ITS   CHARACTERISTIC   ANIMALS.  205 

nearly  completed,  leaving  only  a  narrow  gulf 
running  up  to  the  neighborhood  of  St.  Louis  to 
be  filled  by  modern  detritus,  and  the  peninsula 
of  Florida  to  be  built  by  the  industrious  Coral- 
Workers  of  our  own  period.  The  age  of  the  Al- 
leghany  chain  is  not  yet  positively  determined, 
but  it  was  probably  raised  at  the  close  of  the  Car- 
boniferous epoch.  Up  to  that  time,  only  the 
Lauren tian  Hills,  the  northern  side  of  that  moun- 
tainous triangle  which  now  makes  the  skeleton, 
as  it  were,  of  the  United  States,  existed.  The 
upheaval  of  the  Alleghanies  added  its  eastern 
side,  raising  the  central  part  of  the  continent  so 
as  to  form  a  long  slope  from  the  base  of  the  Air 
leghanies  to  the  Pacific  Ocean;  but  it  was  not 
until  the  Tertiary  Age  that  the  upheaval  of  the 
great  chain  at  the  West  completed  the  triangle^ 
and  transformed  that  wide  westerly  slope  into  the 
Mississippi  Valley,  bounded  on  one  side  by  the 
Alleghanies,  and  on  the  other  by  the  Rocky 
Mountains. 

It  is  my  belief,  founded  upon  the  tropical  char- 
acter of  the  Fauna,  that  a  much  milder  climate 
then  prevailed  over  the  whole  northern  hemis- 
phere than  is  now  known  to  it.  Some  natural- 
ists have  supposed  that  the  presence  of  the  tro- 
pical Mammalia  in  the  Northern  Temperate  Zone 
might  be  otherwise  accounted  for,  —  that  they 
might  have  been  endowed  with  warmer  covering, 


206  THE  TERTIARY  AGE,  AND 

with  thicker  hair  or  fur.  But  I  think  the  sim- 
pler and  more  natural  reason  for  their  existence 
throughout  the  North  is  to  be  found  in  the  differ- 
ence of  climate  ;  and  I  am  the  more  inclined  to 
this  opinion  because  the  Tertiary  animals  gener- 
ally, the  Fishes,  Shells,  etc.,  in  the  same  regions, 
are  more  closely  allied  in  character  to  those  now 
living  in  the  Tropics  than  to  those  of  the  Tem- 
perate Zones.  The  Tertiary  age  may  be  called 
the  geological  summer ;  we  shall  see,  hereafter, 
how  abruptly  it  was  brought  to  a  close. 

One  word  more  as  to  the  relation  of  the  Terti- 
ary Mammalia  to  the  creation  which  preceded 
them.  I  can  only  repeat  here  the  argument  used 
before :  the  huge  quadrupeds  characteristic  of 
these  epochs  make  their  appearance  suddenly, 
and  the  deposits  containing  them  follow  as  im- 
mediately upon  those  of  the  Cretaceous  epoch,  in 
which  no  trace  of  them  occurs,  as  do  those  of  the 
Cretaceous  upon  those  of  the  Jurassic  epoch.  I 
would  remind  the  reader  that  in  the  central  basin 
of  France,  in  which  Cuvier  found  his  first  Palae- 
otherium,  and  which  afterwards  proved  to  have 
been  thickly  settled  by  the  early  Mammalia,  the 
deposits  of  the  Jurassic,  Cretaceous,  and  Tertiary 
epochs  follow  each  other  in  immediate,  direct, 
uninterrupted  succession ;  that  the  same  is  true 
of  other  localities,  in  Germany,  in  Southern  Eu- 
rope, in  England,  where  the  most  complete  col- 


ITS   CHAEACTERISTIC  ANIMALS.  207 

lections  have  been  made  from  all  these  deposits  ; 
and  there  has  never  been  brought  to  light  a  sin- 
gle fact  leading  us  to  suppose  that  any  interme- 
diate forms  have  ever  existed  through  which 
more  recent  types  have  been  developed  out  of 
older  ones.  For  thirty  years  Geology  has  been 
gradually  establishing,  by  evidence  the  fulness 
and  accuracy  of  which  are  truly  amazing,  the 
regularity  in  the  sequence  of  the  geological  for- 
mations, and  distinguishing,  with  ever-increasing 
precision,  the  specific  differences  of  the  animals 
and  plants  contained  in  these  accumulations  of 
past  ages.  These  results  bear  living  testimony 
to  the  wonderful  progress  of  the  kindred  sciences 
of  Geology  and  Palaeontology  in  the  last  half-cen- 
tury; and  the  development-theory  has  but  an 
insecure  foundation  so  long  as  it  attempts  to 
strengthen  itself  by  belittling  the  geological  rec- 
ord, the  assumed  imperfection  of  which,  in  de- 
fault of  positive  facts,  has  now  become  the  favor- 
ite argument  of  its  upholders. 


VIII. 

THE  FORMATION  OP  GLACIERS. 

THE  long  summer  was  over.  For  ages  a  trop- 
ical climate  had  prevailed  over  a  great  part  of 
the  earth,  and  animals  whose  home  is  now  be- 
neath the  Equator  roamed  over  the  world  from 
the  far  South  to  the  very  borders  of  the  Arctics. 
The  gigantic  quadrupeds,  the  Mastodons,  Ele- 
phants, Tigers,  Lions,  Hyenas,  Bears,  whose  re- 
mains are  found  in  Europe  from  its  southern 
promontories  to  the  northernmost  limits  of  Sibe- 
ria and  Scandinavia,  and  in  America  from  the 
Southern  States  to  Greenland  and  the  Melville 
Islands,  may  indeed  be  said  to  have  possessed  the 
earth  in  those  days.  But  their  reign  was  over. 
A  sudden  intense  winter,  that  was  also  to  last  for 
ages,  fell  upon  our  globe ;  it  spread  over  the  very 
countries  where  these  tropical  animals  had  their 
homes,  and  so  suddenly  did  it  come  upon  them 
that  they  were  embalmed  beneath  massesg)f  snow 
ajad  ice,  without  time  even  for  the  decay  which 
follows  death.  The  Elephant  whose  story  was 
told  at  length  in  the  preceding  article  was  by  no 


THE  FORMATION  OF  GLACIERS.  209 

means  a  solitary  specimen  ;  upon  further  inves- 
tigation it  was  found  that  the  disinterment  of 
these  large  tropical  animals  in  Northern  Russia 
and  Asia  was  no  unusual  occurrence.  Indeed, 
their  frequent  discoveries  of  this  kind  had  given 
rise  among  the  ignorant  inhabitants  to  the  sin- 
gular superstition  already  alluded  to,  that  gigan- 
tic moles  lived  under  the  earth,  which  crumbled 
away  and  turned  to  dust  as  soon  as  they  came  to 
the  upper  air.  This  tradition,  no  doubt,  arose 
from  the  fact,  that,  when  in  digging  they  came 
upon  the  bodies  of  these  animals,  they  often 
found  them  perfectly  preserved  under  the  frozen 
ground,  but  the  moment  they  were  exposed  to 
heat  and  light  they  decayed  and  fell  to  pieces  at 
once.  Admiral  Wrangel,  whose  Arctic  explora- 
tions have  been  so  valuable  to  science,  tells  us 
that  the  remains  of  these  animals  are  heaped  up 
in  such  quantities  in  certain  parts  of  Siberia  that 
he  and  his  men  climbed  over  ridges  and  mounds 
consisting  entirely  of  the  bones  of  Elephants,  Rhi- 
noceroses, etc.  From  these  facts  it  would  seem 
that  they  roamed  over  all  these  northern  regions 
in  troops  as  large  and  numerous  as  the  Buffalo 
herds  that  wander  over  our  Western  prairies 
now.  We  are  indebted  to  Russian  naturalists, 
and  especially  to  Rathke,  for  the  most  minute  in- 
vestigations of  these  remains,  in  which  even  the 
texture  of  the  hair,  the  skin,  and  flesh  has  been 


210  THE  FOEMATION  OF  GLACIERS. 

subjected  by  him  to  microscopic  examination  as 
accurate  as  if  made  upon  any  living  animal. 

We  have  as  yet  no  clew  to  the  source  of  this 
great  and  sudden  change  of  climate.  Various 
suggestions  have  been  made,  —  among  others, 
that  formerly  the  inclination  of  the  earth's  axis 
was  greater,  or  that  a  submersion  of  the  conti- 
nents under  water  might  have  produced  a  de- 
cided increase  of  cold ;  but  none  of  these  expla- 
nations are  satisfactory,  and  science  has  yet  to 
find  any  cause  which  accounts  for  all  the  phe- 
nomena connected  with  it.  It  seems,  however, 
unquestionable,  that  since  the  opening  of  the  Ter- 
tiary age  a  cosmic  summer  and  winter  have  suc- 
ceeded each  other,  during  which  a  Tropical  heat 
and  an  Arctic  cold  have  alternately  prevailed 
over  a  great  portion  of  the  present  Temperate 
Zone.  In  <the  so-called  drift  (a  superficial  de- 
posit subsequent  to  the  Tertiaries,  of  the  origin 
of  which  I  shall  speak  presently)  there  are  found 
far  to  the  south  of  their  present  abode  the  re- 
mains of  animals  whose  home  now  is  in  the  Arc- 
tics or  the  coldest  parts  of  the  Temperate  Zones. 
Among  them  are  the  Musk-Ox,  the  Reindeer,  the 
Walrus,  the  Seal,  and  many  kinds  of  Shells  char- 
acteristic of  the  Arctic  regions.  The  northern- 
most part  of  Norway  and  Sweden  is  at  this  day 
the  southern  limit  of  the  Reindeer  in  Europe  ; 
but  their  fossil  remains  are  found  in  large  quan- 


THE  FORMATION  OF   GLACIERS.  211 

titles  in  the  drift  about  the  neighborhood  of  Paris, 
and  quite  recently  they  have  been  traced  even  to 
the  foot  of  the  Pyrenees,  where  their  presence 
would,  of  course,  indicate  a  climate  similar  to 
the  one  now  prevailing  in  Northern  Scandinavia. 
Side  by  side  with  the  remains  of  the  Reindeer 
are  found  those  of  the  European  Marmot,  whose 
present  home  is  in  the  mountains,  about  six  thou- 
sand feet  above  the  level  of  the  sea.  The  occur- 
rence of  these  animals  in  the  superficial  deposits 
of  the  plains  of  Central  Europe,  one  of  which  is 
now  confined  to  the  high  North,  and  the  other 
to  mountain-heights,  certainly  indicates  an  entire 
change  of  climatic  conditions  since  the  time  of 
their  existence.  European  Shells  now  confined 
to  the  Northern  Ocean  are  found  as  fossils  in 
Italy,  —  showing  that,  while  the  present  Arctic 
climate  prevailed  in  the  Temperate  Zone,  that  of 
the  Temperate  Zone  extended  much  farther  south 
to  the  regions  we  now  call  sub-tropical.  In  Amer- 
ica there  is  abundant  evidence  of  the  same  kind ; 
throughout  the  recent  marine  deposits  of  the 
Temperate  Zone,  covering  the  low  lands  above 
tide-water  on  this  continent,  are  found  fossil 
Shells  whose  present  home  is  on  the  shores  of 
Greenland.  It  is  not  only  in  the  Northern  hem- 
isphere that  these  remains  occur,  but  in  Africa 
and  in  South  America,  wherever  there  has  been 
an  opportunity  for  investigation,  the  drift  is  found 


212 


THE  FOKMATION  OF  GLACIERS. 


to  contain  the  traces  of  animals  whose  presence 
indicates  a  climate  many  degrees  colder  than  that 
now  prevailing  there. 

But  these  organic  remains  are  not  the  only  evi- 
dence of  the  geological  winter.  There  are  a  num- 
ber of  phenomena  indicating  that  during  this 
period  two  vast  caps  of  ice  stretched  from  the 
Northern  pole  southward  and  from  the  Southern 
pole  northward,  extending  in  each  case  far  tow- 
ard the  Equator,  —  and  that  ice-fields,  such  as 
now  spread  over  the  Arctics,  covered  a  great  part 
of  the  Temperate  Zones,  while  the  line  of  perpet- 
ual ice  and  snow  in  the  tropical  mountain-ranges 
descended  far  below  its  present  limits.  As  the 
explanation  of  these  facts  has  been  drawn  from 
the  study  of  glacial  action,  I  shall  devote  this  and 
subsequent  articles  to  some  account  of  glaciers 
and  of  the  phenomena  connected  with  them. 

The  first  essential  condition  for  the  formation 
of  glaciers  in  mountain-ranges  is  the  shape  of 
their  valleys.  Glaciers  are  by  no  means  in  pro- 
portion to  the  height  and  extent  of  mountains. 
There  are  many  mountain-chains  as  high  or  high- 
er than  the  Alps,  which  can  boast  of  but  few  and 
small  glaciers,  if,  indeed,  they  have  any.  In  the 
Andes,  the  Rocky  Mountains,  the  Pyrenees,  the 
Caucasus,  the  few  glaciers  remaining  from  the 
great  ice-period  are  insignificant  in  size.  The 
volcanic,  cone-like  shape  of  the  Andes  gives  in- 


THE  FORMATION  OF   GLACIERS.  213 

deed,  but  little  chance  for  the  formation  of  gla- 
ciers, though  their  summits  are  capped  with 
snow.  The  glaciers  of  the  Rocky  Mountains 
have  been  little  explored,  but  it  is  known  that 
they  are  by  no  means  extensive.  In  the  Pyrenees 
there  is  but  one  great  glacier,  though  the  height 
of  these  mountains  is  such,  that,  were  the  shape 
of  their  valleys  favorable  to  the  accumulation  of 
snow,  they  might  present  beautiful  glaciers.  In 
the  Tyrol,  on  the  contrary,  as  well  as  in  Norway 
and  Sweden,  we  find  glaciers  almost  as  fine  as 
those  of  Switzerland,  in  mountain-ranges  much 
lower  than  either  of  the  ajbove-named  chains. 
But  they  are  of  diversified  forms,  and  have  val- 
leys widening  upward  on  the  slope  of  long  crests. 
The  glaciers  on  the  Caucasus  are  very  small  in 
proportion  to  the  height  of  the  range  ;  but  on  the 
northern  side  of  the  Himalaya  there  are  large 
and  beautiful  ones,  while  the  southern  slope  is 
almost  destitute  of  them.  Spitzbergen  and  Green- 
land are  famous  for  their  extensive  glaciers,  com- 
ing down  to  the  sea-shore,  where  huge  masses  of 
ice,  many  hundred  feet  in  thickness,  break  off 
and  float  away  into  the  ocean  as  icebergs.  At 
the  Aletsch  in  Switzerland,  where  a  little  lake 
lies  in  a  deep  cup  between  the  mountains,  with 
the  glacier  coming  down  to  its  brink,  we  have 
these  Arctic  phenomena  on  a  small  scale  ;  a  min- 
iature iceberg  may  often  be  seen  to  break  off  from 


214  THE  FORMATION  OF  GLACIERS. 

the  edge  of  the  larger  mass,  and  float  out  upon 
the  surface  of  the  water.  Icebergs  were  first 
traced  back  to  their  true  origin  by  the  nature  of 
the  land-ice  of  which  they  are  always  composed, 
and  which  is  quite  distinct  in  structure  and  con- 
sistency from  the  marine  ice  produced  by  frozen 
sea-water,  and  called  "ice-flow"  by  the  Arctic 
explorers,  as  well  as  from  the  pond  or  river  ice, 
resulting  from  the  simple  congelation  of  fresh 
water,  the  laminated  structure  of  which  is  in 
striking  contrast  to  the  granular  structure  of 
glacier  ice. 

Water  is  changed  to  ice  at  a  certain  tempera- 
ture under  the  same  law  of  crystallization  by 
which  any  inorganic  bodies  in  a  fluid  state  may 
assume  a  solid  condition,  taking  the  shape  of  per- 
fectly regular  crystals,  which  combine  at  certain 
angles  with  mathematical  precision.  The  frost 
does  not  form  a  solid,  continuous  sheet  of  ice 
over  an  expanse  of  water,  but  produces  crystals, 
little  ice-blades,  as  it  were,  which  shoot  into  each 
other  at  angles  of  thirty  or  sixty  degrees,  form- 
ing the  closest  net-work.  Of  course,  under  the 
process  of  alternate  freezing  and  thawing,  these 
crystals  lose  their  regularity,  and  soon  become 
merged  in  each  other.  But  even  then  a  mass  of 
ice  is  not  continuous  or  compact  throughout,  for 
it  is  rendered  completely  porous  by  air-bubbles, 
the  presence  of  which  is  easily  explained.  Ice 


THE  FORMATION 'OF  GLACIERS.  215 

being  in  a  measure  transparent  to  heat,  the  water 
below  any  frozen  surface  is  nearly  as  susceptible 
to  the  elevation  of  the  temperature  without  as  if 
it  were  in  immediate  contact  with  it.  Such 
changes  of  temperature  produce  air-bubbles,  which 
float  upward  against  the  lower  surface  of  the  ice 
and  are  stranded  there.  At  night  there  may 
come  a  severe  frost ;  new  ice  is  then  formed  be- 
low the  air-bubbles,  and  they  are  thus  caught  and 
imprisoned,  a  layer  of  air-bubbles  between  two 
layers  of  ice,  and  this  process  may  be  continued 
until  we  have  a  succession  of  such  parallel  lay- 
ers, forming  a  body  of  ice  more  or  less  permeated 
with  air.  These  air-bubbles  have  the  power  also 
of  extending  their  own  area,  and  thus  rendering 
the  whole  mass  still  more  porous ;  for,  since  the 
ice  offers  little  or  no  obstacle  to  the  passage  of 
heat,  such  an  air-bubble  may  easily  become  heated 
during  the  day ;  the  moment  it  reaches  a  temper- 
ature above  thirty-two  degrees,  it  melts  the  ice 
around  it,  thus  clearing  a  little  space  for  itself, 
and  rises  through  the  water  produced  by  the  ac- 
tion of  its  own  warmth.  The  spaces  so  formed 
are  so  many  vertical  tubes  in  the  ice,  filled  with 
water,  and  having  an  air-bubble  at  the  upper  ex- 
tremity. 

Ice  of  this  kind,  resulting  from  the  direct  con- 
gelation of  water,  is  easily  recognized  under  all 
circumstances  by  its  regular  stratification,  the 


216  THE  FOEMATION  OF  GLACIERS. 

alternate  beds  varying  in  thickness  according  to 
the  intensity  of  the  cold,  and  its  continuance  be- 
low the  freezing-point  during  a  longer  or  shorter 
period.  Singly,  these  layers  consist  of  irregular 
crystals  confusedly  blended  together,  as  in  large 
masses  of  crystalline  rocks  in  which  a  crystalline 
structure  prevails,  though  regular  crystals  occur 
but  rarely.  The  appearance  of  stratification  is 
the  result  of  the  circumstances  under  which  the 
water  congeals.  The  temperature  varies  much 
more  rapidly  in  the  atmosphere  around  the  earth 
than  in  the  waters  upon  its  surface.  When  the 
atmosphere  above  any  sheet  of  water  sinks  be- 
low the  freezing-point,  there  stretches  over  its 
surface  a  stratum  of  cold  air,  determining  by  its 
intensity  and  duration  the  formation  of  the  first 
stratum  of  ice.  According  to  the  alternations  of 
temperature,  this  process  goes  on  with  varying 
activity  until  the  sheet  of  ice  is  so  thick  that  it 
becomes  itself  a  shelter  to  the  water  below,  and 
protects  it,  to  a  certain  degree,  from  the  cold 
without.  Thus  a  given  thickness  of  ice  may 
cause  a  suspension  of  the  freezing  process,  and 
the  first  ice-stratum  may  even  be  partially  thawed 
before  the  cold  is  renewed  with  such  intensity  as 
to  continue  the  thickening  of  the  ice-sheet  by  the 
addition  of  fresh  layers.  The  strata  or  beds  of 
ice  increase  gradually  in  this  manner,  their  sep- 
aration being  rendered  still  more  distinct  by  the 


THE  FORMATION  OF   GLACIERS.  217 

accumulation  of  air-bubbles,  which,  during  a 
warm  and  clear  day,  may  rise  from  a  muddy 
bottom  in  great  numbers.  In  consequence  of 
these  occasional  collections  of  air-bubbles,  the 
layers  differ,  not  only  in  density  and  closeness, 
but  also  in  color,  the  more  compact  strata  being 
blue  and  transparent,  while  those  containing  a 
greater  quantity  of  air-bubbles  are  opaque  and 
whitish,  like  water  beaten  to  froth. 

A  cake  of  pond-ice,  such  as  is  daily  left  in 
summer  at  our  doors,  if  held  against  the  light 
and  turned  in  different  directions,  will  exhibit 
all  these  phenomena  very  distinctly,  and  we  may 
learn  still  more  of  its  structure  by  watching  its 
gradual  melting.  The  process  of  decomposition 
is  as  different  in  fresh-water  ice  and  in  land-  or 
glacier-ice  as  that  of  their  formation.  Pond-ice, 
in  contact  with  warm  air,  melts  uniformly  over 
its  whole  surface,  the  mass  being  thus  gradually 
reduced  from  the  exterior  till  it  vanishes  com- 
pletely. If  the  process  be  slow,  the-  temperature 
of  the  air-bubbles  contained  in  it  may  be  so  raised 
as  to  form  the  vertical  funnels  or  tubes  alluded 
to  above.  By  the  anastomosing  of  these  funnels, 
the  whole  mass  may  be  reduced  to  a  collection  of 
angular  pyramids,  more  or  less  closely  united  by 
cross-beams  of  ice,  and  it  finally  falls  to  pieces 
when  the  spaces  in  the  interior  have  become  so 
numerous  as  to  render  it  completely  cavernous. 
10 


218  THE  FORMATION  OF   GLACIERS. 

Such  a  breaking-up  of  the  ice  is  always  caused 
by  the  enlargement  of  the  open  spaces  produced 
by  the  elevated  temperature  of  the  air-bubbles, 
these  spaces  being  necessarily  more  or  less  par- 
allel with  one  another,  and  vertical  in  their  posi- 
tion, owing  to  the  natural  tendency  of  the  air- 
bubbles  to  work  their  way  upward  till  they  reach 
the  surface,  where  they  escape.  A  sheet  of  ice, 
of  this  kind,  floating  upon  water,  dissolves  in  the 
same  manner,  melting  wholly  from  the  surface, 
if  the  process  be  sufficiently  rapid,  or  falling  to 
pieces,  if  the  air-bubbles  are  gradually  raised  in 
their  temperature  sufficiently  to  render  the  whole 
mass  cavernous  and  incoherent.  If  we  now  com- 
pare these  facts  with  what  is  known  of  the  struc- 
ture of  land-ice,  we  shall  see  that  the  mode  of 
formation  in  the  two  cases  differs  essentially. 

Land-ice,  of  which  both  the  ice-fields  of  the 
Arctics  and  the  glaciers  consist,  is  produced  by 
the  slow  and  gradual  transformation  of  snow  into 
ice  ;  and  though  the  ice  thus  formed  may  eventu- 
ally be  as  clear  and  transparent  as  the  purest 
pond-  or  river-ice,  its  structure  is  nevertheless  en- 
tirely distinct.  We  may  compare  these  different 
processes  during  any  moderately  cold  winter  in 
the  ponds  and  snow-meadows  immediately  about 
us.  We  need  not  join  an  Arctic  exploring  expe- 
dition, nor  even  undertake  a  more  tempting  trip 
to  the  Alps,  in  order  to  investigate  these  phenom- 


THE   FORMATION   OF  GLACIEES.  219 

ena  for  ourselves,  if  we  have  any  curiosity  to  do 
so.  The  first  warm  day  after  a  thick  fall  of  light, 
dry  snow,  such  as  occurs  in  the  coldest  of  our 
winter  weather,  is  sufficient  to  melt  its  surface. 
As  this  snow  is  porous,  the  water  readily  pene- 
trates it,  having  also  a  tendency  to  sink  by  its 
own  weight,  so  that  the  whole  mass  becomes 
more  or  less  filled  with  moisture  in  the  course  of 
the  day.  During  the  lower  temperature  of  the 
night,  however,  the  water  is  frozen  again,  and  the 
snow  is  now  filled  with  new  ice-particles.  Let 
this  process  be  continued  long  enough,  and  the 
mass  of  snow  is  changed  to  a  .kind  of  ice-gravel, 
or,  if  the  grains  adhere  together,  to  something 
like  what  we  call  pudding-stone,  allowing,  of 
course,  for  the  difference  of  material ;  the  snow, 
which  has  been  rendered  cohesive  by  the  process 
of  partial  melting  and  regelation,  holding  the  ice- 
globules  together,  just  as  the  loose  materials  of 
the  pudding-stone  are  held  together  by  the  cem- 
ent which  unites  them. 

Within  this  mass,  air  is  intercepted  and  held 
inclosed  between  the  particles  of  ice.  The  pro- 
cess by  which  snow-flakes  or  snow-crystals  are 
transformed  into  grains  of  ice,  more  or  less  com- 
pact, is  easily  understood.  It  is  the  result  of  a 
partial  thawing,  under  a  temperature  maintained 
very  nearly  at  thirty-two  degrees,  falling  some- 
times a  little  below,  and  then  rising  a  little  above 


220  THE  FORMATION  OF   GLACIERS. 

the  freezing-point,  and  thus  producing  constant 
alternations  of  freezing  and  thawing  in  the  same 
mass  of  snow.  This  process  amounts  to  a  kind  of 
kneading  of  the  snow,  and  when  combined  with 
the  cohesion  among  the  particles  more  closely 
held  together  in  one  snow-flake,  it  produces  gran- 
ular ice.  Of  course,  the  change  takes  place  grad- 
ually, and  is  unequal  in  its  progress  at  different 
depths  in  the  same  bed  of  recently  fallen  snow. 
It  depends  greatly  on  the  amount  of  moisture 
infiltrating  the  mass,  whether  derived  from  the 
melting  of  its  own  surface,  or  from  the  accumu- 
lation of  dew  or  the  falling  of  rain  or  mist  upon 
it.  The  amount  of  water  retained  within  the 
mass  will  also  be  greatly  affected  by  the  bottom 
on  which  it  rests  and  by  the  state  of  the  atmos- 
phere. Under  a  certain  temperature,  the  snow 
may  only  be  glazed  at  the  surface  by  the  forma- 
tion of  a  thin,  icy  crust,  an  outer  membrane,  as 
it  were,  protecting  the  mass  below  from  a  deeper 
transformation  into  ice  ;  or  it  may  be  rapidly 
soaked  throughout  its  whole  bulk,  the  snow  being 
thus  changed  into  a  kind  of  soft  pulp,  what  we 
commonly  call  slosh,  which,  upon  freezing,  be- 
comes at  once  compact  ice  ;  or,  the  water  sinking 
rapidly,  the  lower  layers  only  may  be  soaked, 
while  the  upper  portion  remains  comparatively 
dry.  But,  under  all  these  various  circumstances, 
frost  will  transform  the  crystalline  snow  into  more 


THE  FORMATION   OF  GLACIERS.  221 

or  less  compact  ice,  the  mass  of  which  will  be 
composed  of  an  infinite  number  of  aggregated 
snow-particles,  very  unequal  in  regularity  of  out- 
line, and  cemented  by  ice  of  another  kind,  derived 
from  the  freezing  of  the  infiltrated  moisture,  the 
whole  being  interspersed  with  air.  Let  the  tem- 
perature rise,  and  such  a  mass,  rigid  before,  will 
resolve  itself  again  into  disconnected  ice-particles, 
like  grains  more  or  less  rounded.  The  process 
may  be  repeated  till  the  whole  mass  is  trans- 
formed into  very  compact,  almost  uniformly 
transparent  and  blue  ice,  broken  only  by  the 
intervening  air-bubbles.  Such  a  mass  of  ice, 
when  exposed  to  a  temperature  sufficiently  high 
to  dissolve  it,  does  not  melt  from  the  surface  and 
disappear  by  a  gradual  diminution  of  its  bulk, 
like  pond-ice,  but  crumbles  into  its  original  gran- 
ular fragments,  each  one  of  which  melts  sepa- 
rately. This  accounts  for  the  sudden  disappear- 
ance of  icebergs,  which,  instead  of  slowly  dissolv- 
ing into  the  ocean,  are  often  seen  to  fall  to  pieces 
and  vanish  at  once. 

Ice  of  this  kind  may  be  seen  forming  every 
winter  on  our  sidewalks,  on  the  edge  of  the  little 
ditches  which  drain  them,  or  on  the  summits  of 
broad  gate-posts  when  capped  with  snow.  Of  such 
ice  glaciers  are  composed ;  but,  in  the  glacier, 
another  element  comes  in  which  we  have  not 
considered  as  yet,  —  that  of  immense  pressure 


222  THE  FORMATION  OF  GLACIERS. 

in  consequence  of  the  vast  accumulations  of  snow 
within  circumscribed  spaces.  We  see  the  same 
effects  produced  on  a  small  scale,  when  snow  is 
transformed  into  a  snowball  between  the  hands. 
Every  boy  who  balls  a  mass  of  snow  in  his  hands 
illustrates  one  side  of  glacial  phenomena.  Loose 
snow,  light  and  porous,  and  pure  white  from  the 
amount  of  air  contained  in  it,  is  in  this  way  pres- 
ently converted  into  hard,  compact,  almost  trans- 
parent ice.  This  change  will  take  place  sooner, 
if  the  snow  be  damp  at  first,  —  but  if  dry,  the 
action  of  the  hand  will  presently  produce  moist- 
ure enough  to  complete  the  process.  In  this  case, 
mere  pressure  produces  the  same  effect  which,  in 
the  cases  we  have  been  considering  above,  was 
brought  about  by  alternate  thawing  and  freezing, 
—  only,  that  in  the  latter  the  ice  is  distinctly 
granular,  instead  of  being  uniform  throughout, 
as  when  formed  under  pressure.  In  the  glaciers 
we  have  the  two  processes  combined.  But  the 
investigators  of  glacial  phenomena  have  consid- 
ered too  exclusively  one  or  the  other :  some  of 
them  attributing  glacial  motion  wholly  to  the 
dilatation  produced  by  the  freezing  of  infiltrated 
moisture  in  the  mass  of  snow  ;  others  accounting 
for  it  entirely  by  weight  and  pressure.  There  is 
yet  a  third  class,  who,  disregarding  the  real  prop- 
ertie^  of  ice,  would  have  us  believe,  that,  because 
tar,  for  instance,  is  viscid  when  it  moves,  there- 


THE  FORMATION  OF   GLACIERS.  223 

fore  ice  is  viscid  because  it  moves.  We  shall 
see  hereafter  that  the  phenomena  exhibited 
in  the  onward  movement  of  glaciers  are  far 
more  diversified  than  has  generally  been  sup- 
posed. 

There  is  no  chain  of  mountains  in  which  the 
shape  of  the  valleys  is  more  favorable  to  the  for- 
mation of  glaciers  than  the  Alps.  Contracted 
at  their  lower  extremity,  these  valleys  widen 
upward,  spreading  into  deep,  broad,  trough-like 
depressions.  Take,  for  instance,  the  valley  of 
Hassli,  which  is  not  more  than  half  a  mile  wide 
where  you  enter  it  above  Meyringen ;  it  opens 
gradually  upward,  till,  above  the  Grimsel,  at  the 
foot  of  the  Finster-Aarhorn,  it  measures  several 
miles  across.  These  huge  mountain-troughs  form 
admirable  cradles  for  the  snow,  which  collects 
in  immense  quantities  within  them,  and,  as  it 
moves  slowly  down  from  the  upper  ranges,  is 
transformed  into  ice  on  its  way,  and  compactly 
crowded  into  the  narrower  space  below.  At  the 
lower  extremity  of  the  glacier  the  ice  is  pure, 
blue,  and  transparent,  but,  as  we  ascend,  it  ap- 
pears less  compact,  more  porous  and  granular, 
assuming  gradually  the  character  of  snow,  till  in 
the  higher  regions  the  snow  is  as  light,  as  shift- 
ing, and  incoherent,  as  the  sand  of  the  desert. 
A  snowstorm  on  a  mountain-summit  is  very  dif- 
ferent from  a  snow-storm  on  the  plain,  on  ac- 


224  THE  FORMATION  OF   GLACIERS. 

count  of  the  different  degrees  of  moisture  in  the 
atmosphere.  At  great  heights,  there  is  never 
dampness  enough  to  allow  the  fine  snow-crystals 
to  coalesce  and  form  what  are  called  "  snow- 
flakes."  I  have  even  stood  on  the  summit  of 
the  Jungfrau  when  a  frozen  cloud  filled  the  air 
with  ice-needles,  while  I  could  see  the  same  cloud 
pouring  down  sheets  of  rain  upon  Lauterbrunnen 
below.  I  remember  this  spectacle  as  one  of  the 
most  impressive  I  have  witnessed  in  my  long 
experience  of  Alpine  scenery.  The  air  immedi- 
ately about  me  seemed  filled  with  rainbow-dust, 
for  the  ice-needles  glittered  with  a  thousand  hues 
under  the  decomposition  of  light  upon  them, 
while  the  dark  storm  in  the  valley  below  offered 
a  strange  contrast  to  the  brilliancy  of  the  upper 
region  in  which  I  stood.  One  wonders  where 
even  so  much  vapor  as  may  be  transformed  into 
the  finest  snow  should  come  from  at  such  heights. 
But  the  warm  winds,  creeping  up  the  sides  of 
the  valleys,  the  walls  of  which  become  heated 
during  the  middle  of  the  day,  come  laden  with 
moisture  which  is  changed  to  a  dry  snow  like 
dust  as  soon  as  it  comes  into  contact  with  the 
intense  cold  above. 

Currents  of  warm  air  affect  the  extent  of  the 
glaciers,  and  influence  also  the  line  of  perpetual 
snow,  which  is  by  no  means  at  the  same  level, 
even  in  neighboring  localities.  The  size  of  gla- 


THE  FORMATION  OF   GLACIERS.  225 

ciers,  of  course,  determines  to  a  great  degree  the 
height  at  which  they  terminate,  simply  because  a 
small  mass  of  ice  will  melt  more  rapidly,  and  at 
a  lower  temperature,  than  a  larger  one.  Thus, 
the  small  glaciers,  such  as  those  of  the  Rothhorn 
or  of  Trift,  above  the  Grimsel,  terminate  at  a 
considerable  height  above  the  plain,  while  the 
Mer  de  Glace,  fed  from  the  great  snow-caldrons 
of  Mont  Blanc,  forces  its  way  down  to  the  bottom 
of  the  valley  of  Chamouni,  and  the  glacier  of 
Grindelwald, ,  constantly  renewed  from  the  deep 
reservoirs  where  the  Jungfrau  hoards  her  vast 
supplies  of  snow,  descends  to  about  four  thou^ 
sand  feet  above  the  sea-level.  But  the  glacier 
of -the  Aar,  though  also  very  large,  comes  to  a 
pause  at  about  six  thousand  feet  above  the  level 
of  the  sea;  for  the  south  wind  from  the  other 
side  of  the  Alps,  the  warm  sirocco  of  Italy,  blows 
across  it,  and  it  consequently  melts  at  a  higher 
level  than  either  the  Mer  de  Glace  or  the  Grin- 
delwald. It  is  a  curious  fact,  that  in  the  valley 
of  Hassli  the  temperature  frequently  rises  instead 
of  falling  as  you  ascend ;  at  the  Grimsel,  the 
temperature  is  at  times  higher  than  at  Meyringen 
below,  where  the  warmer  winds  ar^  not,  felt  so 
directly.  The  glacier  of  Aletsch,  on  Hie-  south- 
ern slope  of  the  Jungfrau,  and  into  which  many 
other  glaciers  enter,  terminates  also  at  a  con- 
siderable height,  because  it  turns  into  the  valley 
10*  o 


226  THE  FORMATION  OF  GLACIERS. 

of  the  Rhone,  through  which  the  southern  winds 
blow  constantly. 

Under  ordinary  conditions,  vegetation  fades  in 
these  mountains  at  the  height  of  six  thousand 
feet,  but,  in  consequence  of  prevailing  winds,  and 
the  sheltering  influence  of  the  mountain-walls, 
there  is  no  uniformity  in  the  limit  of  perpetual 
snow  and  ice.  Where  currents  of  warm  air  are 
very  constant,  glaciers  do  not  occur  at  all,  even 
where  other  circumstances  are  favorable  to  their 
formation.  There  are  valleys  in  the  Alps  far 
above  six  thousand  feet  which  have  no  glaciers, 
and  where  perpetual  snow  is  seen  only  on  their 
northern  sides.  These  contrasts  in  temperature 
lead  to  the  most  wonderful  contrasts  in  the  aspect 
of  the  soil ;  summer  and  winter  lie  side  by  side, 
and  bright  flowers  look  out  from  the  edge  of 
snows  that  never  melt.  Where  the  warm  winds 
prevail,  there  may  be  sheltered  spots  at  a  height  of 
ten  or  eleven  thousand  feet,  isolated  nooks  open- 
ing southward  where  the  most  exquisite  flowers 
bloom  in  the  midst  of  perpetual  snow  and  ice ; 
and  occasionally  I  have  seen  a  bright  little  flower 
with  a  cap  of  snow  over  it  that  seemed  to  be  its 
shelter.  The  flowers  give,  indeed,  a  peculiar 
charm  to  these  high  Alpine  regions.  Occurring 
often  in  beds  of  the  same  kind,  forming  green, 
blue  or  yellow  patches,  they  seem  nestled  close 
together  in  sheltered  spots,  or  even  in  fissures 


THE  FORMATION  OF   GLACIERS.  227 

and  chasms  of  the  rock,  where  they  gather  in 
dense  quantities.  Even  in  the  sternest  scenery 
of  the  Alps  some  sign  of  vegetation  lingers ;  and 
I  remember  to  have  found  a  tuft  of  lichen  grow- 
ing on  the  only  rock  which  pierced  through  the 
ice  on  the  summit  of  the  Jungfrau.  It  was  a 
species  then  unknown  to  botanists,  since  described 
under  the  name  of  Umbelicarus  Higinis.  The  ab- 
solute solitude,  the  intense  stillness  of  the  upper 
Alps  is  most  impressive ;  no  cattle,  no  pasturage, 
no  bird,  nor  any  sound  of  life,  —  and,  indeed, 
even  if  there  were,  the  rarity  of  the  air  in  these 
high  regions  is  such  that  sound  is  hardly  trans- 
missible. The  deep  repose,  the  purity  of  aspect 
of  every  object,  the  snow,  broken  only  by  ridges  of 
angular  rocks,  produce  an  effect  no  less  beautiful 
than  solemn.  Sometimes,  in  the  midst  of  the 
wide  expanse,  one  comes  upon  a  patch  of  the 
so-called  red  snow  of  the  Alps.  At  a  distance, 
one  would  say  that  such  a  spot  marked  some 
terrible  scene  of  blood,  but,  as  you  come  nearer, 
the  hues  are  so  tender  and  delicate,  as  they  fade 
from  deep  red  to  rose,  and  so  die  into  the  pure 
colorless  snow  around,  that  the  first  impression 
is  completely  dispelled.  This  red  snow  is  an 
organic  growth,  a  plant  springing  up  in  such 
abundance  that  it  colors  extensive  surfaces,  just 
as  the  microscopic  plants  dye  our  pools  with 
green  in  the  spring.  It  is  an  Alga  (Protocoites 


228  THE  FORMATION  OF   GLACIERS. 

nivalis)  well  known  in  the  Arctics,  where  it  forms 
wide  fields  in  the  summer. 

With  the  above  facts  before  us  concerning  the 
materials  of  which  glaciers  are  composed,  we  may 
now  proceed  to  consider  their  structure  more 
fully  in  connection  with  their  movements  and  the 
effects  they  produce  on  the  surface  over  which 
they  extend.  It  has  already  been  stated  that  the 
ice  of  the  glaciers  has  not  the  same  appearance 
everywhere,  but  differs  according  to  the  level  at 
which  it  stands.  In  consequence  of  this  we 
distinguish  three  very  distinct  regions  in  these 
frozen  fields,  the  uppermost  of  which,  upon  the 
sides  of  the  steepest  and  highest  slopes  of  the 
mountain-ridges,  consists  chiefly  of  layers  of  snow 
piled  one  above  another  by  the  successive  snow- 
falls of  the  colder  seasons,  anfr  which  would  re- 
main in  uniform  superposition  but  for  the  change 
to  which  they  are  siibjected  in  consequence  of  a 
gradual  downward  movement,  causing  the  mass 
to  descend  by  slow  degrees,  while  new  accumula- 
tions in  the  higher  regions  annually  replace  the 
snow  which  has  been  thus  removed  to  an  inferior 
level.  We  shall  consider  hereafter  the  process  by 
which  this  change  of  position  is  brought  about. 
For  the  present  it  is  sufficient  to  state  that  such 
a  transfer,  b£  which  a  balance  is  preserved  in 
the  distribution  of  the  snow,  takes  place  in  all 
glaciers,  so  that,  instead  of  increasing  indefinitely 


THE  FORMATION  OF  GLACIERS.  229 

in  the  upper  regions,  where  on  account  of  the 
extreme  cold  there  is  little  melting,  they  perma- 
nently preserve  about  the  same  thickness,  being 
yearly  reduced  by  their  downward  motion  in  a 
proportion  equal  to  their  annual  increase  by  fresh 
additions  of  snow.  Indeed,  these  reservoirs  of 
snow  maintain  themselves  at  the  same  level,  much 
as  a  stream,  into  which  many  rivulets  empty, 
remains  within  its  usual  limits  in  consequence  of 
the  drainage  of  the  average  supply.  Of  course, 
very  heavy  rains  or  sudden  thaws  at  certain 
seasons  or  in  particular  years  may  cause  an  oc- 
casional overflow  of  such  a  stream ;  and  irregu- 
larities of  the  same  kind  are  observed  during 
certain  years  or  at  different  periods  of  the  same 
year  in  the  accumulations  of  snow,  in  conse- 
quence of  which  the  successive  strata  may  vary 
in  thickness.  But  in  ordinary  times  layers  from 
six  to  eight  feet  deep  are  regularly  added  annu- 
ally to  the  accumulation  of  snow  in  the  higher 
regions,  —  not  taking  into  account,  of  course,  the 
heavy  drifts  heaped  up  in  particular  localities, 
but  estimating  the  uniform  average  increase  over 
wide  fields.  This  snow  is  gradually  transformed 
into  more  or  less  compact  ice,  passing  through 
an  intermediate  condition  analogous  to  the  slosh 
of  our  roads,  and  in  that  condition  chiefly  occu- 
pies the  upper  part  of  the  extensive  troughs 
into  which  these  masses  descend  from  the  loftier 


230  THE  FOEMATION  OF   GLACIERS. 

heights.  This  region  is  called  the  region  of  the 
nSvS.  It  is  properly  the  birthplace  of  the  gla- 
ciers, for  it  is  here  that  the  transformation  of 
the  snow  into  ice  begins.  The  n£v6  ice,  though 
varying  in  the  degree  of  its  compactness  and 
solidity,  is  always  very  porous  and  whitish  in 
color,  resembling  somewhat  frozen  slosh,  while 
lower  down  in  the  region  of  the  glacier  proper 
the  ice  is  close,  solid,  transparent,  and  of  a  bluish 
tint. 

But  besides  the  difference  in  solidity  and  in  ex- 
ternal appearance,  there  are  also  many  other  im- 
portant changes  taking  place  in  the  ice  of  these 
different  regions,  to  which  we  shall  return  pres- 
ently. Such  modifications  arise  chiefly  from  the 
pressure  to  which  it  is  subjected  in  its  downward 
progress,  and  to  the  alterations,  in  consequence  of 
this  displacement,  in  the  relative  position  of  the 
snow-  and  ice-beds,  as  well  as  to  the  influence  ex- 
erted by  the  form  of  the  valleys  themselves,  not 
only  upon  the  external  aspect  of  the  glaciers,  but 
upon  their  internal  structure  also.  The  surface 
of  a  glacier  varies  greatly  in  character  in  these 
different  regions.  The  uniform  even  surfaces  of 
the  upper  snow-fields  gradually  pass  into  a  more 
undulating  outline,  the  pure  white  fields  become 
strewn  with  dust  and  sand  in  the  lower  levels, 
while  broken  bits  of  stone  and  larger  fragments 
of  rock  collect  upon  them,  which  assume  a  regu- 


THE  FORMATION  OF  GLACIERS.  231 

lar  arrangement,  and  produce  a  variety  of  fea- 
tures most  startling  and  incomprehensible  at  first 
sight,  but  more  easily  understood  when  studied 
iii  connection  with  the  whole  series  of  glacial 
phenomena.  They  are  then  seen  to  be  the  con- 
sequence of  the  general  movement  of  the  glacier, 
and  of  certain  effects  which  the  course  of  the 
seasons,  the  action  of  the  sun,  the  rain,  the  re- 
flected heat  from  the  sides  of  the  valley,  or  the 
disintegration  of  ita  rocky  walls,  may  produce 
upon  the  surface  of  the  ice.  In  the  next  article 
we  shall  consider  in  detail  all  these  phenomena, 
and  trace  them  in  their  natural  connection.  Once 
familiar  with  these  facts,  it  will  not  be  difficult 
correctly  to  appreciate  the  movement  of  the  gla- 
cier and  the  cause  of  its  inequalities.  We  shall 
see,  that,  in  consequence  of  the  greater  or  less 
rapidity  in  the  movement  of  certain  portions  of 
the  mass,  its  centre  progressing  faster  than  its 
sides,  and  the  upper,  middle,  and  lower  regions 
of  the  same  glacier  advancing  at  different  rates, 
the  strata  which  in  the  higher  ranges  of  the 
snow-fields  were  evenly  spread  over  wide  ex- 
panses, become  bent  and  folded  to  such  a  degree 
that  the  primitive  stratification  is  nearly  obliter- 
ated, while  the  internal  mass  of  the  ice  has  also 
assumed  new  features  under  these  new  circum- 
stances. There  is,  indeed,  as  much  difference 
between  the  newly  formed  beds  of  snow  in  the 


232  THE  FORMATION  OF   GLACIERS. 

upper  region  and  the  condition  of  the  ice  at  the 
lower  end  of  a  glacier  as  between  a  recent  deposit 
of  coral  sand  or  a  mud-bed  in  an  estuary  and  the 
metamorphic  limestone  or  clay  slate  twisted  and 
broken  as  they  are  seen  in  the  very  chains  of 
mountains  from  which  the  glaciers  descend.  A 
geologist,  familiar  with  all  the  changes  to  which 
a  bed  of  rock  may  be  subjected  from  the  time 
it  was  deposited  in  horizontal  layers  up  to  the 
time  when  it  was  raised  by  Plutonic  agencies 
along  the  sides  of  a  mountain-ridge,  bent  and  dis- 
torted in  a  thousand  directions,  broken  through 
the  thickness  of  its  mass,  and  traversed  by  innu- 
merable fissures  which  are  themselves  filled  with 
new  materials,  will  best  be  able  to  understand 
how  the  stratification  of  snow  may  be  modified 
by  pressure  and  displacement  so  as  finally  to 
appear  like  a  laminated  mass  full  of  cracks  and 
crevices,  in  which  the  original  stratification  is 
recognized  only  by  the  practical  student.  I  trust 
in  my  next  article  I  shall  be  able  to  explain 
intelligibly  to  my  readers  even  these  extreme 
alterations  in  the  condition  of  the  primitive  snow 
of  the  Alpine  summits. 


IX. 

INTERNAL   STRUCTURE  AND  PROGRES- 
SION OF   GLACIERS. 

IT  is  not  my  intention,  in  these  articles,  to 
discuss  a  general  theory  of  the  glaciers  upon 
physical  and  mechanical  principles.  My  special 
studies,  always  limited  to  Natural  History,  have 
but  indifferently  fitted  me  for  such  a  task,  and 
quite  recently  the  subject  has  been  admirably 
treated  from  this  point  of  view  by  Dr.  Tyndall, 
in  his  charming  volume  entitled  "  Glaciers  of 
the  Alps."  I  have  worked  upon  the  glaciers 
as  an  amateur,  devoting  my  summer  vacations, 
with  friends  desirous  of  sharing  my  leisure,  to 
excursions  in  the  Alps,  for  the  sake  of  relaxation 
from  the  closer  application  of  my  professional 
studies,  and  have  considered  them  especially  in 
their  connection  with  geological  phenomena,  with 
a  view  of  obtaining,  by  means  of  a  thorough 
acquaintance  with  'glaciers  as  they  exist  now, 
some  insight  into  the  glacial  phenomena  of  past 
times,  the  distribution  of  drift,  the  transportation 
of  boulders,  etc.  It  was,  however,  impossible  to 


234  INTERNAL  STRUCTURE  AND 

treat  one  series  of  facts  without  some  reference 
to  the  other ;  lout  such  explanations  as  I  have 
given  of  the  mechanism  of  the  glacier,  in  con- 
nection with  its  structure,  are  presented  in  the 
language  of  the  unprofessional  observer,  without 
any  attempt  at  the  technicalities  of  the  physicist. 
I  do  not  wonder,  therefore,  that  those  who  have 
looked  upon  the  glacier  chiefly  with  reference 
to  the  physical  and  mechanical  principles  in- 
volved in  its  structure  and  movement  should 
have  found  my  Natural  Philosophy  defective.  I 
am  satisfied  with  their  agreement  as  to  my  cor- 
rect observation  of  the  facts,  and  am  the  less 
inclined  to  quarrel  with  the  doubts  thrown  on 
my  theory  since  I  see  that  the  most  eminent 
physicists  of  the  day  do  not  differ  from  me  more 
sharply  than  they  do  from  each  other.  The  facts 
will  eventually  test  all  our  theories,  and  they 
form,  after  all,  the  only  impartial  jury  to  which 
we  can  appeal.  In  the  mean  while,  I  am  not 
sorry  that  just  at  this  moment,  when  recent  in- 
vestigations and  publications  have  aroused  new 
interest  in  the  glaciers,  the  course  of  these  arti- 
cles brings  me  naturally  to  a  discussion  of  the 
subject  in  its  bearing  upon  geological  questions. 
I  shall,  however,  address  myself  especially,  as 
I  have  done  throughout  these  papers,  to  my 
unprofessional  readers,  who,  while  they  admire 
the  glaciers,  may  also  wish  to  form  a  general 


PROGRESSION   OF   GLACIERS.  235 

idea  of  their  structure  and  mode  of  action,  as 
well  as  to  know  something  of  the  important  part 
they  have  played  in  the  later  geological  history 
of  our  earth.  It  would,  indeed,  be  out  of  place, 
were  I  to  undertake  here  a  discussion  of  the  dif- 
ferent views  entertained  by  the  various  students 
who  have  investigated  the  glacier  itself,  among 
whom  Dr.  Tyndall  is  especially  distinguished,  or 
those  of  the  more  theoretical  writers,  among 
whom  Mr.  Hopkins  occupies  a  prominent  position. 
Removed,  as  I  am,  from  all  possibility  of  re- 
newing my  own  observations,  begun  in  1836  and 
ended  in  1845,  I  will  take  this  opportunity  to 
call  the  attention  of  those  particularly  interested 
in  the  matter  to  one  essential  point  with  reference 
to  which  all  other  observers  differ  from  me.  I 
mean  the  stratification  of  the  glacier,  which  I  do 
not  believe  to  be  rightly  understood,  even  at  this 
moment.  It  may  seem  presumptuous  to  dissent 
absolutely  from  the  statements  of  one  who  has. 
seen  so  much  and  so  well  as  Dr.  Tyndall,  on  a 
question  for  the  solution  of  which,  from  the 
physicist's  point  of  view,  his  special  studies  have 
been  a  far  better  preparation  than  mine ;  and 
yet  I  feel  confident  that  I  was  correct  in  describ- 
ing the  stratification  of  the  glacier  as  a  funda- 
mental feature  of  its  structure,  and  the  so-called 
dirt-bands  as  the  margins  of  the  snow-strata 
successively  deposited,  and  in  no  way  originating 


236       INTERNAL  STRUCTURE  AND 

in  the  ice-cascades.  I  shall  endeavor  to  make 
this  plain  to  my  readers  in  the  course  of  the 
present  article.  I  believe,  also,  that  renewed 
observations  will  satisfy  dissenting  observers  that 
there  really  exists  a  net-work  of  capillary  fissures 
extending  throughout  the  whole  glacier,  con- 
stantly closing  and  reopening,  and  constituting 
the  channels  by  means  of  which  water  nitrates 
into  its  mass.  This  infiltration,  also,  has  been 
denied,  in  consequence  of  the  failure  of  some 
experiments  in  which  an  attempt  was  made  to 
introduce  colored  fluids  into  the  glacier.  To  this 
I  can  only  answer,  that  I  succeeded  completely, 
myself,  in  the  self-same  experiments  which  a  later 
investigator  found  impracticable,  and  that  I  see 
no  reason  why  the  failure  of  the  latter  attempt 
should  cast  a  doubt  upon  the  former.  The  ex- 
planation of  the  difference  in  the  result  may, 
perhaps,  be  found  in  the  fact,  that,  as  a  sponge 
gorged  with  water  can  admit  no  more  fluid 
than  it  already  contains,  so  the  glacier,  under 
certain  circumstances,  and  especially  at  noonday 
in  summer,  may  be  so  soaked  with  water  that 
all  attempts  to  pour  colored  fluids  into  it  would 
necessarily  fail.  I  have  stated,  in  my  work  upon 
glaciers,  that  my  infiltration  experiments  were 
chiefly  made  at  night;  and  I  chose  that  time, 
because  I  knew  the  glacier  would  most  readily 
admit  an  additional  supply  of  liquid  from  without 


PEOGEESSION   OF   GLACIEES.  237 

when  the  water  formed  during  the  day  at  its 
surface  and  rushing  over  it  in  myriad  rills  had 
ceased  to  flow. 

While  we  admit  a  number  of  causes  as  af- 
fecting the  motion  of  a  glacier,  —  namely,  the 
natural  tendency  of  heavy  bodies  to  slide  down 
a  sloping  surface,  the  pressure  to  which  the  mass 
is  subjected  forcing  it  onward,  the  infiltration  of 
moisture,  its  freezing  and  consequent  expansion, 
—  we  must  also  remember  that  these  various 
causes,  by  which  the  accumulated  masses  of  snow 
and  ice  are  brought  down  from  higher  to  lower 
levels,  are  not  all  acting  at  all  times  with  the 
same  intensity,  nor  is  their  action  always  the 
same  at  every  point  of  the  moving  mass.  While 
the  bulk  of  snow  and  ice  moves  from  higher  to 
lower  levels,  the  whole  mass  of  the  snow,  in 
consequence  of  its  own  downward  tendency,  is  also 
under  a  strong  vertical  pressure,  arising  from  its 
own  incumbent  weight,  and  that  pressure  is,  of 
course,  greater  at  its  bottom  than  at  its  centre 
or  surface.  It  is  therefore  plain,  that,  inasmuch 
as  the  snow  can  be  compressed  by  its  own  weight, 
it  will  be  more  compact  at  the  bottom  of  such 
an  accumulation  than  at  its  surface,  this  cause 
acting  most  powerfully  at  the  upper  part  of  a 
glacier,  where  the  snow  has  not  yet  been  trans- 
formed into  a  more  solid  icy  mass.  To  these 
two  agencies,  the  downward  tendency  and  the 


238        INTERNAL  STRUCTURE  AND 

vertical  pressure,  must  be  added  the  pressure 
from  behind,  which  is  most  effective  where  the 
mass  is  largest  and  the  amount  of  motion  in  a 
given  time  greatest.  In  the  glacier,  the  mass 
is,  of  course,  largest  in  the  centre,  where  the 
trough  which  holds  it  is  deepest,  and  least  on 
the  margins,  where  the  trough  slopes  upward 
and  becomes  more  shallow.  Consequently,  the 
middle  of  a  glacier  always  advances  more  rapidly 
than  the  sides. 

Were  the  slope  of  the  ground  over  which  it 
passes,  combined  with  the  pressure  to  which  the 
mass  is  subjected,  the  whole  secret  of  the  onward 
progress  of  a  glacier,  it  is  evident  that  the  rate 
of  advance  would  be  gradually  accelerated,  reach- 
ing its  maximum  at  its  lower  extremity,  and 
losing  its  impetus  by  degrees  on  the  higher  levels, 
nearer  the  point  where  the  descent  begins.  This, 
however,  is  not  the  case.  The  glacier  of  the 
Aar,  for  instance,  is  about  ten  miles  in  length ; 
its  rate  of  annual  motion  is  greaetst  near  the 
point  of  junction  of  the  two  great  branches  by 
which  it  is  formed,  diminishing  farther  down, 
and  reaching  a  minimum  at  its  lower  extremity. 
But  in  the  upper  regions,  near  their  origin,  the 
progress  of  these  branches  is  again  gradually 
less. 

Let  us  see  whether  the  next  cause  of  displace- 
ment, the  infiltration  of  moisture,  may  not  in 


PBOGKESSION  OF  GLAC1EES.  239 

some  measure  explain  this  retardation,  at  least 
of  the  lower  part  of  the  glacier.  This  agency, 
like  that  of  the  compression  of  the  snow  by  its 
own  weight  and  the  pressure  from  behind,  is 
most  effective  where  the  accumulation  is  largest. 
In  the  centre,  where  the  body  of  the  mass  is 
greatest,  it  will  imbibe  the  most  moisture.  But 
here  a  modifying  influence  comes  in,  not  suffi- 
ciently considered  by  the  investigators  of  glacial 
structure.  We  have  already  seen  that  snow  and 
ice,  at  different  degrees  of  compactness,  are  not 
equally  permeable  to  moisture.  Above  the  line 
at  which  the  annual  winter  snow  melts,  there 
is,  of  course,  little  moisture ;  but  below  that 
point,  as  soon  as  the  temperature  rises  in  summer 
sufficiently  to  melt  the  surface,  the  water  easily 
penetrates  the  mass,  passing  through  it  more 
readily  where  the  snow  is  lightest  and  least  com- 
pact,—  in  short,  where  it  has  not  begun  its 
transformation  into  ice.  A  summer's  day  sends 
countless  rills  of  water  trickling  through  such  a 
mass  of  snow.  If  the  snow  be  loose  and  porous 
throughout,  the  water  will  pass  through  its  whole 
thickness,  accumulating  at  the  bottom,  so  that 
the  lower  portion  of  the  mass  will  be  damper, 
more  completely  soaked  with  water,  than  the 
upper  part ;  if,  on  the  contrary,  in  consequence 
of  the  process  previously  described,  alternate 
melting  and  freezing  combined  with  pressure, 


240        INTERNAL  STRUCTURE  AND 

the  mass  has  assumed  the  character  of  icy  snow, 
it  does  not  admit  moisture  so  readily,  and  still 
farther  down,  where  the  snow  is  actually  trans- 
formed into  pure  compact  ice,  the  amount  of 
surface-water  admitted  into  its  structure  will, 
of  course,  be  greatly  diminished.  There  may, 
however,  be  conditions  under  which  even  the 
looser  snow  is  comparatively  impervious  to  water ; 
as,  for  instance,  when  rain  falls  upon  a  snow-field 
which  has  been  long  under  a  low  temperature, 
and  an  ice-crust  is  formed  upon  its  surface,  pre- 
venting the  water  from  penetrating  below.  Ad- 
mitting, as  I  believe  we  must,  that  the  water 
thus  introduced  into  the  snow  and  ice  is  one 
of  the  most  powerful  agents  to  which  its  motion 
is  due,  we  must  suppose  that  it  has  a  twofold 
influence,  since  its  action  when  fluid  and  when 
frozen  would  be  different.  When  fluid,  it  would 
contribute  to  the  advance  of  the  mass  in  propor- 
tion to  its  quantity  ;  but  when  frozen,  its  expan- 
sion would  produce  a  displacement  corresponding 
to  the  greater  volume  of  ice  as  compared  with 
water ;  add  to  this  that  while  trickling  through 
the  mass  it  will  loosen  and  displace  the  particles 
of  already  consolidated  ice.  I  have  already  said 
that  I  did  not  intend  to  trespass  on  the  ground 
of  the  physicist,  and  I  will  not  enter  here  upon 
any  discussion  as  to  the  probable  action  of  the 
laws  of  hydrostatic  pressure  and  dilatation  in 


PROGRESSION   OF   GLACIERS.  241 

this  connection.  I  will  only  state,  that,  so  far 
as  my  own  observation  goes,  the  movement  of 
the  glacier  is  most  rapid  where  the  greatest 
amount  of  moisture  is  introduced  into  the  mass, 
and  that  I  believe  there  must  be  a  direct  relation 
between  these  two  facts.  If  I  am  right  in  this, 
then  the  motion,  so  far  as  it  is  connected  with 
infiltrated  moisture  or  with  the  dilatation  caused 
by  the  freezing  of  that  moisture,  will,  of  course, 
be  most  rapid  where  the  glacier  is  most  easily 
penetrated  by  water,  namely,  in  the  region  of 
the  neve  and  in  the  upper  portion  of  the  glacier- 
troughs,  where  the  nev&  begins  to  be  transformed 
into  more  or  less  porous  ice.  This  cause  also 
accounts,  in  part  at  least,  for  another  singular 
fact  in  the  motion  of  the  glacier:  that,  in  its 
higher  levels,  where  its  character  is  more  porous 
and  the  water  entering  at  the  surface  sinks  read- 
ily to  the  bottom,  there  the  bottom  seems  to 
move  more  rapidly  than  the  superficial  parts  of 
the  mass,  whereas,  at  the  lower  end  of  the  glacier, 
in  the  region  of  the  compact  ice,  where  the  in- 
filtration of  the  water  at  the  bottom  is  at  its  min- 
imum, while  the  disintegrating  influences  at  the 
surface  admit  of  infiltration  to  a  certain  limited 
depth,  there  the  motion  is  greater  near  the  sur- 
face than  toward  the  bottom.  But,  under  all 
circumstances,  it  is  plain  that  the  various  causes 
producing  motion,  gravitation,  pressure,  infiltra- 
11  p 


242        INTEENAL  STRUCTURE  AND 

tion  of  water,  frost,  will  combine  to  propel  the 
mass  at  a  greater  rate  along  its  axis  than  near 
its  margins.  For  details  concerning  the  facts  of 
the  case,  I  would  refer  to  my  work  entitled  "  Sys- 
tdme  Glaciaire." 

We  will  next  consider  the  stratification  of  the 
glacier.  I  have  stated,  in  my  introductory  re- 
marks, that  I  consider  this  to  be  one  of  its  pri- 
mary and  fundamental  features,  and  I  confess, 
that,  after  a  careful  examination  of  the  results 
obtained  by  my  successors  in  the  field  of  glacial 
phenomena,  I  still  believe  that  the  original  strat- 
ification of  the  mass  of  snow  from  which  the  gla- 
cier arises  gives  us  the  key  to  many  facts  of  its 
internal  structure.  The  ultimate  features  results 
ing  from  this  connection  are  so  exceedingly  in- 
tricate and  entangled  that  their  relation  is  not 
easily  explained.  Nevertheless,  I  trust  my  read- 
ers will  follow  me  in  this  Alpine  excursion,  where 
I  shall  try  to  smooth  the  asperities  of  the  road  for 
them  as  much  as  possible. 

Imparted  to  it,  at  the  very  beginning  of  its 
formation,  by  the  manner  in  which  snow  accu- 
mulates, and  retained  through  all  its  transfor- 
mations, the  stratification  of  a  glacier,  however 
distorted,  and  at  times  almost  obliterated,  re- 
mains, notwithstanding,  as  distinct  to  one  who 
is  acquainted  with  all  its  phases,  as  is  the  strat- 


PBOGKESSION  OF   GLACIERS.  243 

ified  character  of  metamorphic  rocks  to  the  skil- 
ful geologist,  even  though  they  may  be  readily 
mistaken  for  plutonic  masses  by  the  common  ob- 
server. Indeed,  even  those  secondary  features, 
as  the  dirt-bands,  for  instance,  which  we  shall 
see  to  be  intimately  connected  with  snow-strata, 
and  which  eventually  become  so  prominent  as  to 
be  mistaken  for  the  cause  of  the  lines  of  stratifi- 
cation, do  nevertheless  tend,  when  properly  un- 
derstood, to  make  the  evidence  of  stratification 
more  permanent,  and  to  point  out  its  primitive 
lines. 

On  the  plains,  in  our  latitude,  we  rarely  have 
the  accumulated  layers  of  several  successive  snow- 
storms preserved  one  above  another.  We  can, 
therefore,  hardly  imagine  with  what  distinctness 
the  sequence  of  such  beds  is  marked  in  the  upper 
Alpine  regions.  The  first  cause  of  this  distinc- 
tion between  the  layers  is  the  quality  of  the  snow 
when  it  falls,  then  the  immediate  changes  it 
undergoes  after  its  deposit,  then  the  falling  of 
mist  or  rain  upon  it,  and  lastly  and  most  efficient 
of  all,  the  accumulation  of  dust  upon  its  surface. 
One  who  has  not  felt  the  violence  of  a  storm  in 
the  high  mountains,  and  seen  the  clouds  of  dust 
and  sand  carried  along  with  the  gusts  of  wind 
passing  over  a  mountain-ridge  and  sweeping 
through  the  valley  beyond,  can  hardly  conceive 
that  not  only  the  superficial  aspect  of  a  glacier, 


244  INTERNAL  STRUCTURE  AND 

but  its  internal  structure  also,  can  be  materially 
affected  by  such  a  cause.  Not  only  are  dust  and 
sand  thus  transported  in  large  quantities  to  the 
higher  mountain  regions,  but  leaves  are  frequent- 
ly found  strewn  upon  the  upper  glacier,  and  even 
pine-cones,  and  maple-seeds  flying  upward  on  their 
spread  wings,  are  scattered  thousands  of  feet  above 
and  many  miles  beyond  the  forests  where  they 
grow. 

This  accumulation  of  sand  and  dust  goes  on 
all  the  year  round,  but  the  amount  accumulated 
over  one  and  the  same  surface  is  greatest  during 
the  summer,  when  the  largest  expanse  of  rocky 
wall  is  bare  of  snow,  and  its  loose  soil  dried  by 
the  heat  so  as  to  be  easily  dislodged.  This  sum- 
mer deposit  of  loose  inorganic  materials,  light 
enough  to  be  transported  by  the  wind,  forms  the 
main  line  of  division  between  the  snow  of  one 
year  and  the  next,  though  only  that  of  the  last 
year  is  visible  for  its  whole  extent.  Those  of 
the  preceding  years,  as  we  shall  see  hereafter, 
exhibit  only  their  edges  cropping  out  lower 
down  one  beyond  another,  being  brought  suc- 
cessively to  lower  levels  by  the  onward  motion 
of  the  glacier. 

Other  observers  of  the  glacier,  Professor  Forbes 
and  Dr.  Tyndall,  have  noticed  only  the  edges  of 
these  seams,  and  called  them  dirt-bands.  Look- 
ing upon  them  as  merely  superficial  phenomena, 


PROGRESSION  OF  GLACIERS  245 

they  have  given  explanations  of  their  appearance 
which  I  hold  to  be  quite  untenable.  Indeed,  to 
consider  these  successive  lines  of  dirt  on  the  gla- 
cier as  limited  only  to  its  surface,  and  to  explain 
them  from  that  point  of  view,  is  much  as  if  a 
geologist  were  to  consider  the  lines  presented  by 
the  strata  on  a  cut  through  a  sedimentary  mass 
of  rock  as  representing  their  whole  extent,  and 
to  explain  them  as  a  superficial  deposit  due  to 
external  causes. 

A  few  more  details  may  help  to  make  this  state- 
ment clearer  to  my  readers.  Let  us  imagine  that 
a  fresh  layer  of  snow  has  fallen  in  these  moun- 
tain regions,  and  that  a  deposit  of  dirt  has  been 
scattered  over  its  surface,  which,  if  any  moisture 
arises  from  the  melting  of  the  snow  or  from  the 
falling  of  rain  or  mist,  will  become  more  closely 
compacted  with  it.  The  next  snow-storm  depos- 
its a  fresh  bed  of  snow,  separated  from  the  one 
below  it  by  the  sheet  of  dust  just  described,  and 
this  bed  may,  in  its  turn,  receive  a  like  deposit. 
For  greater  ease  and  simplicity  of  explanation,  I 
speak  here  as  if  each  successive  snow-layer  were 
thus  indicated ;  of  course  this  is  not  literally  true, 
because  snow-storms  in  the  winter  may  follow 
each  other  so  fast  that  there  is  no  time  for  such 
a  collection  of  foreign  materials  upon  each  newly 
formed  surface.  But  whenever  such  a  fresh  snow- 
bed,  or  accumulation  of  beds,  remains  with  its 


246        INTERNAL  STRUCTURE  AND 

surface  exposed  for  some  time,  such  a  deposit  of 
dirt  will  inevitably  be  found  upon  it.  This  pro- 
cess may  go  on  till  we  have  a  number  of  succes- 
sive snow-layers  divided  from  each  other  by  thin 
sheets  of  dust.  Of  course,  such  seams,  marking 
the  stratification  of  snow,  are  as  permanent  and 
indelible  as  the  seams  of  coarser  materials  al- 
ternating with  the  finest  mud  in  a  sedimentary 
rock. 

The  gradual  progress  of  a  glacier,  which, 
though  more  rapid  in  summer  than  in  winter,  is 
never  intermitted,  changes  the  relation  of  these 
beds  to  each  other.  Their  lower  edge  is  annu- 
ally cut  off  at  a  certain  level,  because  the  snow 
deposited  every  winter  melts  with  the  coming 
summer,  up  to  a  certain  line,  determined  by  the 
local  climate  of  the  place.  But  although  the 
snow  does  not  melt  above  this  line,  we  have  seen, 
in  the  preceding  article,  that  it  is  prevented  from 
accumulating  indefinitely  in  the  higher  regions 
by  its  own  tendency  to  move  down  to  the  lower 
valleys,  and  crowding  itself  between  their  walls, 
thus  to  force  its  way  toward  the  outlet  below. 
Now,  as  this  movement  is  very  gradual,  it  is  evi- 
dent that  there  must  be  a  perceptible  difference 
in  the  progress  of  the  successive  layers,  the  lower 
and  older  ones  getting  the  advance  of  the  upper 
and  more  recent  ones:  that  is,  when  the  snow 
that  has  covered  the  face  of  the  country  during 


PROGRESSION  OF  GLACIERS.  247 

one  winter  melts  away  from  the  glacier  up  to  the 
so-called  snow-line,  there  will  be  seen  cropping 
out  below  and  beyond  that  line  the  layers  of  the 
preceding  years,  which  are  already  partially  trans- 
formed into  ice,  and  have  become  a  part  of  the 
frozen  mass  of  the  glacier  with  which  they  are 
moving  onward  and  downward.  In  the  autumn, 
when  the  dust  of  a  whole  season  has  been  accu- 
mulated upon  the  service  of  the  preceding  win- 
ter's snow,  the  extent  of  the  layer  which  year 
after  year  will  henceforth  crop  out  lower  down, 
as  a  dirt-band,  may  best  be  appreciated. 

Beside  the  snow-layers  and  the  sheets  of  dust 
alternating  with  them,  there  is  still  another  feat- 
ure of  the  horizontal  and  parallel  structure  of  the 
mass  in  immediate  connection  with  those  above 
considered.  I  allude  to  the  layers  of  pure  com- 
pact ice  occurring  at  different  intervals  between 
the  snow-layers.  In  July,  when  the  snow  of  the 
preceding  winter  melts  up  to  the  line  of  perpet- 
ual snow,  the  masses  above,  which  are  to  with- 
stand the  summer  heat  and  become  part  of  the 
glacier  forever,  or  at  least  until  they  melt  away 
at  the  lower  end,  begin  to  undergo  the  changes 
through  which  all  snow  passes  before  it  acquires 
the  character  of  glacial  ice.  It  thaws  at  the  sur- 
face, is  rained  upon,  or  condenses  moisture,  thus 
becoming  gradually  soaked,  and  after  assuming 
the  granular  character  of  n£v6-iGQ9  it  ends  in  be- 


248  INTERNAL  STRUCTURE  AND 

ing  transformed  into  pure  compact  ice.  Toward 
the  end  of  August,  or  early  in  September,  when 
the  nights  are  already  very  cold  in  the  Alps,  but 
prior  to  the  first  permanent  autumnal  snow-falls, 
the  surface  of  these  masses  becomes  frozen  to  a 
greater  or  less  depth,  varying,  of  course,  accord- 
ing to  temperature.  These  layers  of  ice  become 
numerous  and  are  parallel  to  each  other,  like  the 
layers  of  ice  formed  from  slosh.  Such  crusts  of 
ice  I  have  myself  observed  again  and  again  upon 
the  glacier.  This  stratified  snowy  ice  is  now  the 
bottom  on  which  the  first  autumnal  snow-falls  ac- 
cumulate. These  sheets  of  ice  may  be  formed 
not  only  annually  before  the  winter  snows  set  in, 
but  may  recur  at  intervals  whenever  water  accu- 
mulating upon  an  extensive  snow-surface,  either 
in  consequence  of  melting  or  of  rain,  is  frozen 
under  a  sharp  frost  before  another  deposit  of 
snow  takes  place.  Or  suppose  a  fresh  layer  of 
light  porous  snow  to  have  accumulated  above  one, 
the  surface  of  which  has  already  been  slightly 
glazed  with  frost ;  rain  or  dew,  falling  upon  the 
upper  one,  will  easily  penetrate  it ;  but  when  it 
reaches  the  lower  one,  it  will  be  stopped  by  the 
film  of  ice  already  formed,  and,  under  a  suffi- 
ciently low  temperature,  it  will  be  frozen  between 
the  two.  This  result  may  be  frequently  noticed 
in  winter,  on  the  plains,  where  sudden  changes 
of  temperature  take  place. 


PROGRESSION  OF   GLACIERS.  249 

There  is  still  a  third  cause,  to  which  the  same 
result  may  possibly  be  due,  and  to  which  I  shall 
refer  at  greater  length  hereafter ;  but  as  it  has 
not,  like  the  preceding  ones,  been  the  subject  of 
direct  observation,  it  must  be  considered  as  hy- 
pothetical. The  admirable  experiments  of  Dr. 
Tyndall  have  shown  that  water  may  be  gener- 
ated in  ice  by  pressure,  and  it  is  therefore  possi- 
ble that  at  a  lower  depth  in  the  glacier,  where 
the  incumbent  weight  of  the  mass  above  is  suffi- 
ient  to  produce  water,  the  water  thus  accu- 
mulated may  be  frozen  into  ice-layers.  But  this 
depends  so  much  upon  the  internal  tempera- 
ture of  the  glacier,  about  which  we  know  little 
beyond  a  comparatively  superficial  depth,  that  it 
cannot  at  present  afford  a  sound  basis  even  for 
conjecture. 

There  are,  then,  in  the  upper  snow-fields  three 
kinds  of  horizontal  deposits :  the  beds  of  snow, 
the  sheets  of  dust,  and  the  layers  of  ice,  alternat- 
ing with  each  other.  If,  now,  there  were  no  mod- 
ifying circumstances  to  change  the  outline  and 
surface  of  the  glacier,  —  if  it  moved  on  uninter- 
ruptedly through  an  open  valley,  the  lower  lay- 
ers, forming  the  mass,  getting  by  degrees  the  ad- 
vance of  the  upper  ones,  our  problem  would  be 
simple  enough.  We  should  then  have  a  longi- 
tudinal mass  of  snow,  enclosed  between  rocky 
walls,  its  surface  crossed  by  straight  transverse 
11* 


250  INTEENAL  STRUCTURE  AND 

lines  marking  the  annual  additions  to  the  glacier, 
as  in  the  adjoining  figure. 

But  that  mass  of  snow,  before 
it  reaches  the  outlet  of  the  val- 
ley, is  to  be  compressed,  con- 
torted, folded,  rent  in  a  thou- 
sand directions.  The  beds  of 
snow,  which  in  the  upper  rang- 
es of  the  mountain  were  spread 
out  over  broad,  open  surfaces, 
are  to  be  crowded  into  compar- 
atively circumscribed  valleys,  to 
force  and  press  themselves  through  narrow  passes, 
alternately  melting  and  freezing,  till  they  pass  from 
the  condition  of  snow  into  that  of  ice,  to  undergo, 
in  short,  constant  transformations,  by  which  the 
primitive  stratifications  will  be  extensively  modi- 
fied. In  the  first  place,  the  more  rapid  motion  of 
the  centre  of  the  glacier,  as  compared  with  the 
margins,  will  draw  the  lines  of  stratification  down- 
ward toward  the  middle  faster  than  at  the  sides. 
Accurate  measurements  have  shown  that  the  axis 
of  a  glacier  may  move  ten-  or  twenty-fold  more 
rapidly  than  its  margins.  This  is  not  the  place 
to  introduce  a  detailed  account  of  the  experiments 
made  to  ascertain  this  result;  but  I  would  refer 
those  who  are  interested  in  the  matter  to  the 
measurements  given  in  my  "  Syst£me  Glaciaire," 
where  it  will  be  seen  that  the  middle  may  move 


PROGRESSION  OF  GLACIERS.  251 

at  a  rate  of  two  hundred  feet  a  year,  while  the 
margins  may  not  advance  more  than  fifteen  or 
ten  feet,  or  even  less,  in  the  same  time.  These 
observations  of  mine  have  the  advantage  over 
those  of  other  observers,  that,  while  they  embrace 
the  whole  extent  of  the  glacier,  transversely  as 
well  as  in  its  length,  they  cover  a  period  of  sev- 
eral successive  years,  instead  of  being  limited  to 
summer  campaigns  and  a  few  winter  observations. 
The  consequence  of  this  mode  of  progressing  will 
be  that  the  straight  lines  drawn  transversely  across 
the  surface  of  the  glacier 
above  will  be  gradually 
changed  to  curved  ones 
below.  After  a  few  years, 
such  a  line  will  appear  on 
the  surface  of  the  glacier 
like  a  crescent,  with  the 
bow  turned  downward, 
within  which,  above,  are 
other  crescents,  less  and 
less  sharply  arched  up  to 
the  last  year's  line,  which 
may  be  again  straight 
across  the  snow-field.  (See 
the  subjoined  figure,  which 
represents  a  part  of  the 
glacier  of  the  Lauter-Aar.) 

Thus  the  glacier  records  upon  its  surface  its 


252        INTERNAL  STRUCTURE  AND 

annual  growth  and  progress,  and  registers  also 
the  inequality  in  the  rate  of  advance  between 
the  axis  and  the  sides. 

But  these  are  only  surface  phenomena.  Let 
us  see  what  will  be  the  effect  upon  the  internal 
structure.  We  must  not  forget,  in  considering  the 
changes  taking  place  within  glaciers,  the  shape  of 
the  valleys  which  contain  them.  A  glacier  lies  in 
a  deep  trough,  and  the  tendency  of  the  mass  will 
be  to  sink  towards  its  deeper  part,  and  to  fold  in- 
ward and  downward,  if  subjected  to  a  strong  lat- 
eral pressure,  —  that  is,  to  dip  toward  the  centre 
and  slope  upward  along  the  sides,  following  the 
scoop  of  the  trough.  If,  now,  we  examine  the  face 
of  a  transverse  cut  in  the  glacier,  we  find  it  trav- 
ersed by  a  number  of  lines,  vertical  in  some  places, 
more  or  less  oblique  in  others,  and  frequently 
these  lines  are  joined  together  at  the  lower  ends, 
forming  loops,  some  of  which  are  close  and  ver- 
tical, while  others  are  quite  open.  These  lines 
are  due  to  the  folding  of  the  strata  in  consequence 
of  the  lateral  pressure  they  are  subjected  to  when 
crowded  into  the  lower  course  of  the  valleys,  and 
the  difference  in  their  dip  is  due  to  the  greater  or 
less  force  of  that  pressure.  The  wood-cut  on  the 
next  page  represents  a  transverse  cut  across  the 
Lauter-Aar  and  the  Finster-Aar,  the  two  princi- 
pal tributaries  to  the  great  Aar  glacier,  and  in- 
cludes also  a  number  of  small  lateral  glaciers 


PEOGEESSION   OF  GLACIEES.  258 

which  join  them.  The  beds  on  the  left,  which 
dip  least,  and  are  only  folded  gently  downward, 
forming  very  open  loops,  are  those  of  the  Lauter- 
Aar,  where  the  lateral  pressure  is  comparatively 
slight.  Those  which  are  almost  vertical  belong 
in  part  to  the  several  small  trib- 
utary glaciers,  which  have  been 
crowded  together  and  very  strong- 
ly compressed,  and  partly  to  the 
Finster-Aar.  The  close  uniform 
vertical  lines  in  this  wood-cut 
represent  a  different  feature  in 
the  structure  of  the  glacier,  called 
blue  bands,  to  which  I  shall  re- 
fer presently.  These  loops  or 
lines  dipping  into  the  internal 
mass  of  the  glacier  have  been  the 
subject  of  much  discussion,  and 
various  theories  have  been  re- 
cently proposed  respecting  them. 
I  believe  them  to  be  caused,  as 
I  have  said,  by  the  snow-layers, 
originally  deposited  horizontally, 
but  afterwards  folded  into  a  more 
or  less  vertical  position,  in  con- 
sequence of  the  lateral  pressure 
brought  to  bear  upon  them.  The 
sheets  of  dust  and  of  ice  alter- 
nating with  the  snow-strata  are 


254  INTERNAL  STRUCTURE  AND 

of  course  subjected  to  the  same  action,  and  are 
contorted,  bent,  and  folded  by  the  same  lateral 
pressure. 

Dr.  Tyndall  has  advanced  the  view  that  the 
lines  of  apparent  stratification,  and  especially  the 
dirt-bands  across  the  surface  of  the  glacier,  are 
due  to  ice-cascades  :  that  is,  the  glacier,  passing 
over  a  sharp  angle,  is  cracked  across  transversely 
in  consequence  of  the  tension,  and  these  rents, 
where  the  back  of  the  glacier  has  been  succes- 
sively broken,  when  recompacted,  cause  the  trans- 
verse lines,  the  dirt  being  collected  in  the  furrow 
formed  between  the  successive  ridges.  Unfor- 
tunately for  his  theory,  the  lines  of  stratification 
constantly  occur  in  glaciers  where  no  such  ice- 
falls  are  found.  His  principal  observations  upon 
this  subject  were  made  on  the  Glacier  du  G£ant, 
where  the  ice-cascade  is  very  remarkable.  The 
lines  may  perhaps  be  rendered  more  distinct  on 
the  Glacier  du  Ge*ant  by  the  cascade,  and  neces- 
sarily must  be  so,  if  the  rents  coincide  with  the 
limit  at  which  the  annual  snow-line  is  nearly 
straight  across  the  glacier.  In  the  region  of  the 
Aar  glacier,  however,  where  my  own  investiga- 
tions were  made,  all  the  tributaries  entering  into 
the  larger  glaciers  are  ribbed  across  in  this  way, 
and  most  of  them  join  the  main  trunk  over  uni- 
form slopes,  without  the  slightest  cascade. 

It  must  be  remembered  that  these  surface-phe- 


PROGRESSION  OF  GLACIERS.  ,     255 

nomena  of  the  glacier  are  not  to  be  seen  at  all 
times,  nor  under  all  conditions.  During  the  first 
year  of  my  sojourn  on  the  glacier  of  the  Aar,  I 
was  not  aware  that  the  stratification  of  its  tribu- 
taries was  so  universal  as  I  afterward  found  it  to 
be  ;  the  primitive  lines  of  the  strata  are  often  so 
far  erased  that  they  are  not  perceptible,  except 
under  the  most  favorable  circumstances.  But 
when  the  glacier  has  been  washed  clean  by  rain, 
and  the  light  strikes  upon  it  in  the  right  direc- 
tion, these  lines  become  perfectly  distinct,  where, 
under  different  conditions,  they  could  not  be  dis- 
cerned at  all.  After  passing  many  summers  on 
the  same  glacier,  renewing  my  observations  year 
after  year  over  the  same  localities,  I  can  confi- 
dently state  that  not  only  do  the  lines  of  stratifi- 
cation exist  throughout  the  great  glacier  of  the 
Aar,  but  in  all  its  tributaries  also.  Of  course, 
they  are  greatly  modified  in  the  lower  part  of  the 
glacier  by  the  intimate  fusion  of  its  tributaries, 
and  by  the  circumstance  that  their  movement, 
primarily  independent,  is  merged  in  the  move- 
ment of  the  main  glacier  embracing  them  all. 
We  have  seen  that  not  only  does  the  centre  of  a 
glacier  move  more  rapidly  than  its  sides,  but  that 
the  deeper  mass  of  the  glacier  also  moves  at  a 
different  rate  from  its  more  superficial  portion. 
My  own  observations  (for  the  details  of  which 
I  would  again  refer  the  reader  to  my  "  SystSme 


256  INTERNAL  STRUCTURE  AND 

Glaciaire  "  )  show  that  in  the  higher  part  of  the 
glacier,  especially  in  the  region  of  the  neve,  the 
bottom  of  the  mass  seems  to  move  more  rapidly 
than  the  surface,  while  lower  down,  toward  the 
terminus  of  the  glacier,  the  surface, 
on  the  contrary,  moves  faster  than 
the  bottom.*  The  annexed  wood-cut 
exhibits  a  longitudinal  section  of  the 
glacier,  in  which  this  difference  in 
the  motion  of  the  upper  and  lower 
portions  of  the  mass  is  represented, 
the  beds  being  almost  horizontal  in 
the  upper  snow-fields,  while  their  low- 
*er  portion  slopes  more  rapidly  down- 
ward in  the  neve  region,  and  toward 
the  lower  end  the  upper  portion  takes 
the  lead,  and  advances  more  rapidly 
than  the  lower. 

I  presented  these  results  for  the 
first  time  in  two  letters,  dated  Octo- 
ber 9th,  1842,  which  were  published 
in  a  German  periodical,  the  Jahrbuch 
of  Leonhard  and  Bronn.  The  last 
three  wood-cuts  introduced  above,  the 
transverse  and  longitudinal  sections 
of  the  glacier,  as  well  as  that  repre- 
senting the  concentric  lines  of  strat- 
ification on  the  surface,  are  the  iden- 
tical ones  contained  in  those  communications. 


PROGRESSION  OF   GLACIERS.  257 

These  papers  seem  to  have  been  overlooked  by  con- 
temporary investigators,  and  I  may  be  permitted 
to  translate  here  a  passage  from  one  of  them,  since 
it  sums  up  the  results  of  the  inequality  of  motion 
throughout  the  glacier  and  its  influence  on  the 
primitive  stratification  of  the  mass  in  as  few  words 
and  as  correctly  as  I  could  give  them  to-day, 
twenty  years  later :  —  "  Combining  these  views, 
it  appears  that  the  glacier  may  be  represented  as 
composed  of  concentric  shells  which  arise  from 
the  parallel  strata  of  the  upper  region  by  the  fol- 
lowing process.  The  primitively  regular  strata 
advance  into  gradually  narrower  and  deeper  val- 
leys, in  consequence  of  which  the  margins  are 
raised,  while  the  middle  is  bent  not  only  down- 
ward, but,  from  its  more  rapid  motion,  forward 
also,-  so  that  they  assume  a  trough-like  form  in 
the  interior  of  the  mass.  Lower  down,  the  gla- 
cier is  worn  by  the  surrounding  air,  and  assumes 
the  peculiar  form  characteristic  of  its  lower 
course."  The  last  clause  alludes  to  another  se- 
ries of  facts,  which  we  shall  examine  in  a  future 
article,  when  we  shall  see  that  the  heat  of  the 
walls  in  the  lower  part  of  its  course  melts  the 
sides  of  the  glacier,  so  that,  instead  of  following 
the  trough-like  shape  of  the  valley,  it  becomes 
convex,  arching  upward  in  the  centre  and  sink- 
ing at  the  margins. 

I  have  dwelt  thus  long,  and  perhaps  my  read- 

Q 


258  INTERNAL  STRUCTURE  AND 

ers  may  think  tediously,  upon  this  part  of  my 
subject,  because  the  stratification  of  the  glacier 
has  been  constantly  questioned  by  the  more  re^ 
cent  investigators  of  glacial  phenomena,  and  has 
indeed  been  set  aside  as  an  exploded  theory.  They 
consider  the  lines  of  stratification,  the  dirt-bands, 
and  the  seams  of  ice  alternating  with  the  more 
porous  snow,  as  disconnected  surface-phenomena, 
while  I  believe  them  all  to  be  intimately  con- 
nected together  as  primary  essential  features  of 
the  original  mass. 

There  is  another  feature  of  glacial  structure, 
inrtimately  connected,  by  similarity  of  position  and 
aspect,  .with  the  stratification,  which  has  greatly 
perplexed  the  students  of  glacial  phenomena.  I 
allude  to  the  so-called  blue  bands,  or  bands  of 
infiltration,  also  designated  as  veined  structure, 
ribboned  or  laminated  structure,  marginal  struc- 
ture, and  longitudinal  structure.  The  difficulty 
lies,  I  believe,  in  the  fact  that  two  very  distinct 
structures,  that  of  the  stratification  and  the  blue 
bands,  are  frequently  blended  together  in  certain 
parts  of  the  glacier  in  such  a  manner  as  to  seem 
identical,  while  elsewhere  the  one  is  prominent 
and  the  other  subordinate,  and  vice  versd.  Ac- 
cording to  their  various  opportunities  of  investi- 
gation, observers  have  either  confounded  the  two, 
believing  them  to  be  the  same,  or  some  have  over- 


PROGRESSION  OF  GLACIERS.  259 

looked  the  one  and  insisted  upon  the  other  as  the 
prevailing  feature,  while  that  very  feature  has 
been  absolutely  denied  again  by  others  who  have 
seen  its  fellow  only,  and  taken  that  to  be  the 
prominent  and  important  fact  in  this  peculiar 
structural  character  of  the  ice. 

We  have  already  seen  how  the  stratification  of 
the  glacier  arises,  accompanied  by  layers  of  dust 
and  other  material  foreign  to  the  glacier,  and 
how  blue  bands  of  compact  ice  may  be  formed 
parallel  to  the  surface  of  these  strata.  We  have 
also  seen  how  the  horizontality  of  these  strata 
may  be  modified  by  pressure  till  they  assume  a 
position  within  the  mass  of  the  glacier,  varying 
from  a  slightly  oblique  inclination  to  a  vertical 
one.  Now,  while  the  position  of  the  strata  be- 
comes thus  altered  under  pressure,  other  chan- 
ges take  place  in  the  constitution  of  the  ice  itself* 

Before  attempting  to  explain  how  these  chan- 
ges take  place,  let  us  consider  the  facts  them- 
selves. The  mass  of  the  glacier  ice  is  traversed 
by  thin  bands  of  compact  blue  ice,  these  bands 
being  very  numerous  along  the  margins  of  the 
glacier,  where  they  constitute  what  Dr.  Tyndall 
calls  marginal  structure,  and  still  more  crowded 
along  the  line  upon  which  two  glaciers  unite, 
where  he  has  called  it  longitudinal  structure.  In 
the  latter  case,  where  the  extreme  pressure  re- 
sulting from  the  junction  of  two  glaciers  has  ren- 


260        INTERNAL  STRUCTURE  AND 

dered  the  strata  nearly  vertical,  these  blue  bands 
follow  their  trend  so  closely  that  it  is  almost  im- 
possible to  distinguish  one  from  the  other.  It 
will  be  seen,  on  referring  to  the  wood-cut  on  page 
253,  where  the  close,  uniform,  vertical  lines  rep- 
resent the  true  veined  structure,  that  at  several 
points  of  that  section  the  lines  of  stratification 
run  so  nearly  parallel  with  them,  that,  were  the 
former  not  drawn  more  strongly,  they  could  not 
be  easily  distinguished  from  the  latter.  Along  the 
margins,  also,  in  consequence  of  the  retarded  mo- 
tion, the  blue  bands  and  the  lines  of  stratification 
run  nearly  parallel  with  each  other,  both  follow- 
ing the  sides  of  the  trough  in  which  they  move. 

Undoubtedly,  in  both  these  instances,  we  have 
two  kinds  of  blue  bands,  namely :  those  formed 
primitively  in  a  horizontal  position,  indicating 
seams  of  stratification,  and  those  which  have 
arisen  subsequently  in  connection  with  the  move- 
ment of  the  whole  mass,  which  I  have  occasion- 
ally called  bands  of  infiltration,  as  they  appeared 
to  me  to  be  formed  by  the  infiltration  and  freez- 
ing of  water.  The  fact  that  these  blue  bands  are 
most  numerous  where  two  glaciers  are  crowded 
together  into  a  common  bed  naturally  suggests 
pressure  as  their  cause.  And  since  the  beautiful 
experiments  of  Dr.  Tyndall  have  illustrated  the 
internal  liquefaction  of  ice  by  pressure,  it  be- 
comes highly  probable  that  his  theory  of  the  ori- 


PROGRESSION  OF  GLACIERS.  261 

gin  of  these  secondary  blue  bands  is  the  true  one. 
He  suggests  that  layers  of  water  may  be  formed 
in  the  glacier  at  right  angles  with  the  pressure, 
and  pass  into  a  state  of  solid  ice  upon  the  re- 
moval of  that  pressure,  the  pressure  being  of 
course  relieved  in  proportion  to  the  diminution 
in  the  body  of  the  ice  by  compression.  The  num- 
ber of  blue  bands  diminishes  as  we  recede  from 
the  source  of  the  pressure,  —  few  only  being 
formed,  usually  at  right  angles  with  the  surfaces 
qf  stratification,  in  the  middle  of  a  glacier,  half- 
way between  its  sides.  If  they  are  caused  by 
pressure,  this  diminution  of  their  number  toward 
the  middle  of  the  glacier  would  be  inevitable, 
since  the  intensity  of  the  pressure  naturally  fades 
as  we  recede  from  the  motive  power. 

Dr.  Tyndall  also  alludes  to  another  structure 
of  the  same  kind,  which  he  calls  transverse  struc- 
ture, where  the  blue  bands  extend  in  crescent- 
shaped  curves,  more  or  less  arched,  across  the 
surface  of  the  glacier.  Where  these  do  not  co- 
incide with  the  stratification,  they  are  probably 
formed  by  vertical  pressure  in  connection  with 
the  unequal  movement  of  the  mass. 

With  these  facts  before  us,  it  seems  to  me  plain 
that  the  primitive  blue  bands  arise  with  the  strat- 
ification of  the  snow  in  the  very  first  formation 
of  the  glacier,  while  the  secondary  blue  bands  are 
formed  subsequently,  in  consequence  of  the  on- 


262        INTERNAL  STRUCTURE  AND 

ward  progress  of  the  glacier  and  the  pressure  to 
which  it  is  subjected.  The  secondary  blue  bands 
intersect  the  planes  of  stratification  at  every  pos- 
sible angle,  and  may  therefore  seem  identical 
with  the  stratification  in  some  places,  while  in 
others  they  cut  it  at  right  angles.  It  has  been 
objected  to  my  theory  of  glacial  structure,  that 
I  have  considered  the  so-called  blue  bands  as  a 
superficial  feature  when  compared  with  the  strat- 
ification. And  in  a  certain  sense  this  is  true ; 
since,  if  my  views  are  correct,  the  glacier  exists 
and  is  in  full  life  and  activity  before  the  second- 
ary blue  bands  arise  in  it,  whereas  the  stratifi- 
cation is  a  feature  of  its  embryo  condition,  al- 
ready established  in  the  accumulated  snow  before 
it  begins  its  transformation  into  glacier-ice.  In 
other  words,  the  veined  structure  of  the  glacier 
is  not  a  primary  structural  feature  of  its  whole 
mass,  but  the  result  of  various  local  influences 
acting  upon  the  constitution  of  the  ice  ;  the  mar- 
ginal structure  resulting  from  the  resistance  of 
the  sides  of  the  valley  to  the  onward  movement 
of  the  glacier,  the  longitudinal  structure  arising 
from  the  pressure  caused  by  two  glaciers  uniting 
in  one  common  bed,  the  transverse  structure  be- 
ing produced  by  vertical  pressure,  in  consequence 
of  the  weight  of  the  mass  itself  and  the  increased 
rate  of  motion  at  the  centre. 
In  the  nev6  fields,  where  the  strata  are  still 


PROGRESSION  OF  GLACIERS.  263 

horizontal,  the  few  blue  bands  observed  are  per- 
pendicular to  the  strata  of  snow,  and  therefore 
also  perpendicular  to  the  blue  seams  of  ice  and 
the  sheets  of  dust  alternating  with  them.  Upon 
the  sides  of  the  glacier  they  are  more  or  less  par- 
allel to  the  slopes  of  the  valley ;  along  the  line 
of  junction  of  two  glaciers  they  follow  the  verti- 
cal trend  of  the  axis  of  the  mass  ;  while  at  inter- 
mediate positions  they  are  more  or  less  oblique. 
Along  the  outcropping  edges  of  the  strata,  on  the 
surface  of  the  glacier,  they  follow  more  or  less 
the  dip  of  the  strata  themselves  ;  that  is  to  say, 
they  are  more  or  less  parallel  with  the  dirt-bands. 
In  conclusion,  I  would  recommend  future  inves- 
tigators to  examine  the  glaciers,  with  reference 
to  the  distribution  of  the  blue  bands,  after  heavy 
rains  and  during  foggy  days,  when  the  surface  is 
freed  from  the  loose  materials  and  decomposed 
fragments  of  ice  resulting  from  the  prolonged  ac- 
tion of  the  sun. 

The  most  important  facts,  then,  to  be  consid- 
ered with  reference  to  the  motion  of  the  glacier 
are  as  follows.  First,  that  the  rate  of  advance 
between  the  axis  and  the  margins  of  a  glacier 
differs  in  the  ratio  of  about  ten  to  one  and  even 
less  ;  that  is  to  say,  when  the  centre  is  advancing 
at  a  rate  of  two  hundred  and  fifty  feet  a  year,  the 
motion  toward  the  sides  may  be  gradually  dimin- 


264  INTERNAL  STRUCTURE  AND 

ished  to  two  hundred,  one  hundred  and  fifty,  one 
hundred,  fifty  feet,  and  so  on,  till  nearest  the 
margin  it  becomes  almost  inappreciable.  Sec- 
ondly, the  rate  of  motion  is  not  the  same  through- 
out the  length  of  the  glacier,  the  advance  being 
greatest  about  half-way  down  in  the  region  of  the 
neve,  and  diminishing  in  rapidity  both,  above  and 
below ;  thus  the  onward  motion  in  the  higher 
portion  of  a  glacier  may  not  exceed  twenty  to 
fifty  feet  a  year,  while  it  reaches  its  maximum 
of  some  two  hundred  and  fifty  feet  annually  in 
the  neve  region,  and  is  retarded  again  toward  the 
lower  extremity,  where  it  is  reduced  to  about 
one  fourth  of  its  maximum  rate.  Thirdly,  the 
glacier  moves  at  different  rates  throughout  the 
thickness  of  its  mass  ;  toward  the  lower  extrem- 
ity of  the  glacier  the  bottom  is  retarded,  and  the 
surface  portion  moves  faster,  while  in  the  upper 
region  the  bottom  seems  to  advance  more  rapidly. 
I  say  seems ,  because  upon  this  latter  point  there 
are  no  positive  measurements,  and  it  is  only  in- 
ferred from  general  appearances,  while  the  for- 
mer statement  has  been  demonstrated  by  accu- 
rate experiments.  Remembering  the  form  of  the 
troughs  in  which  the  glaciers  arise,  that  they 
have  their  source  in  expansive,  open  fields  of 
snow  and  ne've,  and  that  these  immense  accumu- 
lations move  gradually  down  into  ever-narrowing 
channels,  though  at  times  widening  again  to  con- 


PROGRESSION  OF  GLACIERS.  265 

tract  anew,  their  surface  wasting  so  little  from 
external  influences  that  they  advance  far  below 
the  line  of  perpetual  snow  without  any  sensible 
diminution  in  size,  it  is  evident  that  an  enormous 
pressure  must  have  been  brought  to  bear  upon 
them  before  they  could  have  been  packed  into 
the  lower  valleys  through  which  they  descend. 

Physicists  seem  now  to  agree  that  pressure  is 
the  chief  agency  in  the  motion  of  glaciers.  No 
doubt,  all  the  facts  point  that  way ;  but  it  now 
becomes  a  matter  of  philosophical  interest  to  de- 
termine in  what  direction  it  acts  most  powerfully, 
and  upon  this  point  glacialists  are  by  no  means 
agreed.  The  latest  conclusion  seems  to  be,  that 
the  weight  of  the  advancing  mass  is  itself  the 
efficient  cause  of  the  motion.  But  while  this  is 
probably  true  in  the  main,  other  elements  tend- 
ing to  the  same  result,  and  generally  overlooked 
by  investigators,  ought  to  be  taken  into  considera- 
tion ;  and  before  leaving  the  subject,  I  would  add 
a  few  words  upon  infiltration  in  this  connection. 

The  weight  of  the  glacier,  as  a  whole,  is  about 
the  same  all  the  year  round.  If,  therefore,  press- 
ure, resulting  from  that  weight,  be  the  all-con- 
trolling agency,  its  progress  should  be  uniform 
during  the  whole  year,  or  even  greatest  in  win- 
ter, which  is  by  no  means  the  case.  By  a  series 
of  experiments,  I  have  ascertained  that  the  on- 
ward movement,  whatever  be  its  annual  average, 
12 


266  INTERNAL  STRUCTURE  AND 

is  accelerated  in  spring  and  early  summer.  The 
average  annual  advance  of  the  glacier  being,  at 
a  given  point,  at  the  rate  of  about  two  hundred 
feet,  its  average  summer  advance,  at  the  same 
point,  will  be  at  a  rate  of  two  hundred  and  fifty 
feet,  while  its  average  rate  of  movement  in  win- 
ter will  be  about  one  hundred  and  fifty  feet.  This 
can  be  accounted  for  only  by  the  increased  press- 
ure due  to  the  large  accession  of  water  trickling 
in  spring  and  early  summer  into  the  interior 
through  the  network  of  capillary  fissures  per- 
vading the  whole  mass.  The  unusually  large  in- 
filtration of  water  at  that  season  is  owing  to  the 
melting  of  the  winter  snow.  Careful  experiments 
made  on  the  glacier  of  the  Aar,  respecting  the 
water  thus  accumulating  on  the  surface,  pene- 
trating its  mass,  and  finally  discharged  in  part 
at  its  lower  extremity,  fully  confirm  this  view. 
Here,  then,  is  a  powerful  cause  of  pressure  and 
consequent  motion,  quite  distinct  from  the  per- 
manent weight  of  the  mass  itself,  since  it  oper- 
ates only  at  certain  seasons  of  the  year.  In  mid- 
winter, when  the  infiltration  is  reduced  to  a 
minimum,  the  motion  is  least.  The  water  thus 
introduced  into  the  glacier  acts,  as  we  have  seen 
above,  in  various  ways  :  by  its  weight,  by  loosen- 
ing the  particles  of  snow  and  ice  through  which 
it  trickles,  and  by  freezing  and  consequent  ex- 
pansion, at  least  within  the  limits  and  during  the 


PROGEESSION  OF  GLACIERS.  267 

season  at  which  the  temperature  of  the  glacier 
sinks  below  32°  Fahrenheit.  The  simple  fact, 
that  in  the  spring  the  glacier  swells  on  an  aver- 
age to  about  five  feet  more  than  its  usual  level, 
shows  how  important  this  infiltration  must  be. 
I  can  therefore  only  wonder  that  other  glacialists 
have  given  so  little  weight  to  this  fact.  It  is  ad- 
mitted by  all,  that  the  waste  of  a  glacier  at  its 
surface,  in  consequence  of  evaporation  and  melt- 
ing,  amounts  to  about  nine  or  ten  feet  in  a  year. 
At  this  rate  of  diminution,  a  glacier,  even  one 
thousand  feet  in  thickness,  could  not  advance 
during  a  single  century  without  being  exhausted. 
The  water  supplied  by  infiltration  no  doubt  re- 
pairs the  loss  to  a  great  degree.  Indeed,  the 
lower  part  of  the  glacier  must  be  chiefly  main- 
tained from  this  source,  since  the  annual  increase 
from  the  fresh  accumulations  of  snow  is  felt  only 
above  the  snow-line,  below  which  the  yearly  snow 
melts  away  and  disappears.  In  a  complete  the- 
ory of  the  glaciers,  the  effect  of  so  great  an  ac- 
cession of  plastic  material  cannot  be  overlooked. 
I  now  come  to  some  points  in  the  structure  of 
the  glacier,  the  consideration  of  which  is  likely 
to  have  a  decided  influence  in  settling  the  con- 
flicting views  respecting  their  motion.  The  ex- 
periments of  Faraday  concerning  regelation,  and 
the  application  of  the  facts  made  known  by  the 
great  English  physicist  to  the  theory  of  the  glar 


268       INTERNAL  STRUCTURE  AND 

ciers,  as  first  presented  by  Dr.  Tyndall  in  his 
admirable  work,  show  that  fragments  of  ice  with 
moist  surfaces  are  readily  reunited  under  press- 
ure into  a  solid  mass.  It  follows  from  these  ex- 
periments, that  glacier-ice,  at  a  temperature  of 
32°  Fahrenheit,  may  change  its  form  and  pre- 
serve its  continuity  during  its  motion,  in  virtue 
of  the  pressure  to  which  it  is  subjected.  The 
statement  is,  that,  when  two  pieces  of  ice  with 
moistened  surfaces  are  placed  in  contact,  they 
become  cemented  together  by  the  freezing  of  a 
film  of  water  between  them,  while,  when  the  ice  is 
below  32°  Fahrenheit,  and  therefore  dry,  no  effect 
of  the  kind  can  be  produced.  The  freezing  was 
also  found  to  take  place  under  water ;  and  the 
result  was  the  same,  even  when  the  water  into 
which  the  ice  was  plunged  was  as  hot  as  the 
hand  can  bear. 

The  fact  that  ice  becomes  cemented  under 
these  circumstances  is  fully  established,  and  my 
own  experiments  have  confirmed  it  to  the  fullest 
extent.  I  question,  however,  the  statement,  that 
regelation  takes  place  by  the  freezing  of  a  film  of 
water  between  the  fragments.  I  never  have  been 
able  to  detect  any  indication  of  the  presence  of 
such  a  film,  and  am,  therefore,  inclined  to  con- 
sider this  result  as  akin  to  what  takes  place  when 
fragments  of  moist  clay  or  marl  are  pressed  to- 
gether and  thus  reunited.  When  examining  beds 


PEOGEESSION  OF  GLACIEES.  269 

of  clay  and  marl,  or  even  of  compact  limestone, 
especially  in  large  mountain  masses,  I  have  fre- 
quently observed  that  the  rock  presents  a  net- 
work of  minute  fissures  pervading  the  whole, 
without  producing  a  distinct  solution  of  continu- 
ity, though  generally  determining  the  lines  ac- 
cording to  which  it  breaks  under  sudden  shocks. 
The  network  of  capillary  fissures  pervading  the 
glacier  may  fairly  be  compared  to  these  rents  in 
hard  rocks ;  with  this  difference,  however,  that  in 
ice  they  are  more  permeable  to  water  than  in  stone. 
How  this  network  of  capillary  fissures  is  formed 
has  not  been  ascertained  by  direct  observation. 
Following,  however,  the  transformation  of  the 
snow  and  n£ve  into  compact  ice,  it  is  easily  con- 
ceived that  the  porous  mass  of  snow,  as  it  falls 
in  the  upper  regions  of  the  Alps,  and  in  the 
broad  caldrons  in  which  the  glaciers  properly 
originate,  cannot  pass  into  solid  ice,  by  the  pro- 
cess described  in  a  former  article,  without  retain- 
ing within  itself  larger  or  smaller  quantities  of 
air.  This  air  is  finally  surrounded  from  all 
sides  by  the  cementation  of  the  granules  of  neve, 
through  the  freezing  of  the  water  that  penetrates 
it.  So  enclosed,  the  bubbles  of  air  are  subject  to 
the  same  compression  as  the  ice  itself,  and  be- 
come more  flattened  in  proportion  as  the  snow 
has  been  more  fully  transformed  into  compact 
ice.  As  long  as  the  transformation  of  snow  into 


270  INTERNAL  STRUCTURE  AND 

ice  is  not  complete,  a  rise  of  its  temperature  to 
32°  Fahrenheit,  accompanied  with  thawing,  re- 
duces it  at  once  again  to  the  condition  of  loose 
grains  of  neve ;  but  when  more  compact,  it  al- 
ways presents  the  aspect  of  a  mass  composed 
of  angular  fragments,  wedged  and  dovetailed  to- 
gether, and  separated  by  capillary  fissures,  the 
flattened  air-bubbles  trending  in  the  same  direc- 
tion in  each  fragment,  but  varying  in  their  trend 
from  one  fragment  to  another.  There  is,  more- 
over, this  important  point  to  notice,  —  that,  the 
older  the  nSve,  the  larger  are  its  composing  gran- 
ules ;  and  where  n£v£  passes  into  porous  ice, 
small  angular  fragments  are  mixed  with  rounded 
w^-granules,  the  angular  fragments  appearing 
larger  and  more  numerous,  and  the  nev£-grenL- 
ules  fewer,  in  proportion  as  the  neve-icQ  has  un- 
dergone most  completely  its  transformation  into 
compact  glacier-ice.  These  facts  show  conclu- 
sively that  the  dimensions  and  form  of  the  nevg- 
granules,  the  size  and  shape  of  the  angular  frag- 
ments, the  porosity  of  the  ice,  the  arrangement 
of  its  capillary  fissures,  and  the  distribution  and 
compression  of  the  air-bubbles  it  contains,  are  all 
connected  features,  mutually  dependent.  Wheth- 
er the  transformation  of  snow  into  ice  be  the  re- 
sult of  pressure  only,  or,  as  I  believe,  quite  as 
much  the  result  of  successive  thawings  and  freez- 
ings, these  structural  features  can  equally  be  pro- 


PEOGEESSION  OF  GLACIERS.  271 

duced,  and  exhibit  these  relations  to  one  another. 
It  may  be,  moreover,  that,  when  the  glacier  is  at 
a  temperature  below  32°,  its  motion  produces  ex- 
tensive fissuration  throughout  the  mass. 

Now  that  water  pervades  this  network  of  fis- 
sures in  the  glacier  to  a  depth  not  yet  ascer- 
tained, my  experiments  upon  the  glacier  of  the 
Aar  have  abundantly  proved ;  and  that  the  fis- 
sures themselves  exist  at  a  depth  of  two  hundred 
and  fifty  feet  I  also  know,  from  actual  observa- 
tion. All  this  can,  of  course,  take  place,  even 
if  the  internal  temperature  of  the  glacier  never 
should  fall  below  32°  Fahrenheit ;  and  it  has  ac- 
tually been  assumed  that  the  temperature  within 
the  glacier  does  not  fall  below  this  point,  and 
that,  therefore,  no  phenomena,  dependent  upon 
a  greater  degree  of  cold,  can  take  place  beyond  a 
very  superficial  depth,  to  which  the  cold  outside 
may  be  supposed  to  penetrate.  I  have,  however, 
observed  facts  which  seem  to  me  irreconcilable 
with  this  assumption.  In  the  first  place,  a  ther- 
mometrograph  indicating  — 2°  Centigrade  (about 
28°  Fahrenheit)  at  a  depth  of  a  little  over  two 
metres,  that  is,  about  six  feet  and  a  half,  has 
been  recovered  from  the  interior  of  the  glacier  of 
the  Aar,  while  all  my  attempts  to  thaw  out  other 
instruments  placed  in  the  ice  at  a  greater  depth 
utterly  failed,  owing  to  the  circumstance,  that, 
after  being  left  for  some  time  in  the  glacier,  they 


272        INTERNAL  STRUCTURE  AND 

were  invariably  frozen  up  in  newly  formed  water- 
ice,  entirely  different  in  its  structure  from  the 
surrounding  glacier-ice.  This  freezing  could  not 
have  taken  place,  did  the  mass  of  the  glacier 
never  fall  below  32°  Fahrenheit.  And  this  is 
not  the  only  evidence  of  hard  frost  in  the  interior 
of  the  glaciers.  The  innumerable  large  walls  of 
water-ice,  which  may  be  seen  intersecting  their 
mass  in  every  direction  and  to  any  depth  thus 
far  reached,  show  that  water  freezes  in  their  in- 
terior. It  cannot  be  objected,  that  this  is  merely 
the  result  of  pressure  ;  since  the  thin  fluid  seams, 
exhibited  under  pressure  in  the  interesting  ex- 
periments of  Dr.  Tyndall,  and  described  in  his 
work  under  the  head  of  Crystallization  and  In- 
ternal Liquefaction,  cannot  be  compared  to  the 
large,  irregular  masses  of  water-ice  found  in  the 
interior  of  the  glacier,  to  which  I  here  allude. 

In  the  absence  of  direct  thermometric  obser- 
vations, from  which  the  lowest  internal  temper- 
ature of  the  glacier  could  be  determined  with 
precision  in  all  its  parts,  we  are  certainly  justi- 
fied in  assuming  that  every  particle  of  water-ice 
found  in  the  glacier,  the  formation  of  which  can- 
not be  ascribed  to  the  mere  fact  of  pressure,  is 
due  to  the  influence  of  a  temperature  inferior  to 
32°  Fahrenheit  at  the  time  of  its  consolidation. 
The  fact  that  the  temperature  in  winter  has  been 
proved  by  actual  experiment  to  fall  as  low  as  28° 


PKOGKESSION  OF   GLACIEES.  273 

Fahrenheit,  that  is,  four  degrees  below  the  freez- 
ing-point, at  a  depth  of  six  feet  below  a  thick 
covering  of  snow,  though  not  absolutely  conclu- 
sive as  to  the  temperature  at  a  greater  depth,  is 
certainly  very  significant. 

Under  these  circumstances,  it  is  not  out  of 
place  to  consider  through  what  channels  the  low 
temperature  of  the  air  surrounding  the  glacier 
may  penetrate  into  the  interior.  '  The  heavy  cold 
air  may  of  course  sink  from  the  surface  into 
every  large  open  space,  such  as  the  crevasses, 
large  fissures,  and  moulins  or  mill-like  holes  to 
be  described  in  a  future  article  ;  it  may  also  pen- 
etrate with  the  currents  which  ingulf  themselves 
under  the  glacier,  or  it  may  enter  through  its 
terminal  vault,  or  through  the  lateral  openings 
between  the  walls  of  the  valley  and  the  ice.  In- 
deed, if  all  the  spaces  in  the  mass  of  the  glacier, 
not  occupied  by  continuous  ice,  could  be  graphi- 
cally represented,  I  believe  it  would  be  seen  that 
cold  air  surrounds  the  glacier-ice  itself  in  every 
direction,  so  that  probably  no  masses  of  a  greater 
thickness  than  that  already  known  to  be  perme- 
able to  cold  at  the  surface  would  escape  this  con- 
tact with  the  external  temperature.  If  this  be 
the  case,  it  is  evident  that  water  may  freeze  in 
any  part  of  the  glacier. 

To  substantiate  this  position,  which,  if  sus- 
tained, would  prove  that  the  dilatation  of  the 

12*  B 


274       INTERNAL  STRUCTURE  AND 

mass  of  the  glacier  is  an  essential  element  of 
its  motion,  I  may  allude  to  several  other  well- 
known  facts.  The  loose  snow  of  the  upper  re- 
gions is  gradually  transformed  into  compact 
ice.  The  experiments  of  Dr.  Tyndall  prove 
that  this  may  be  the  result  of  pressure ;  but 
in  the  region  of  the  n£v£  it  is  evidently  ow- 
ing to  the  transformation  of  the  snow-flakes 
into  ice  by  repeated  melting  and  freezing,  for 
it  takes  place  in  the  uppermost  layers  of  the 
snow,  where  pressure  can  have  no  such  effect,  as 
well  as  in  its  deeper  beds.  I  take  it  for  granted, 
also,  that  no  one,  familiar  with  the1  presence  of 
the  numerous  ice-seams  parallel  to  the  layers 
of  snow  in  these  upper  regions  of  the  glacier, 
can  doubt  that  they,  as  well  as  the  nev£,  are 
the  result  of  frost.  But  be  this  as  it  may, 
the  difference  between  the  porous  ice  of  the 
upper  region  of  the  glacier  and  the  compact  blue 
ice  of  its  lower  track  seems  to  me  evidence 
direct  that  at  times  the  whole  mass  must  as- 
sume the  rigidity  imparted  to  it  by  a  temper- 
ature inferior  to  the  freezing-point.  We  know 
that  at  32°  Fahrenheit,  regelation  renders  the 
mass  continuous,  and  that  it  becomes  brittle  only 
at  a  temperature  below  this.  In  other  words, 
the  ice  can  break  up  into  a  mass  of  disconnected 
fragments,  such  as  the  capillary  fissures  and  the 
infiltration-experiments  described  in  my  "  Sys- 


PROGEESSION  OF  GLACIERS.  275 

t£me  Glaciaire "  show  to  exist,  only  when  it 
is  below  32°  Fahrenheit.  If  it  be  contended 
that  ice  at  32°  does  break,  and  that  therefore 
the  whole  mass  of  the  glacier  may  break  at 
that  temperature,  setting  aside  the  contradic- 
tion to  the  facts  of  regelation  which  such  an 
assumption  involves,  I  would  refer  to  Dr. 
Tyndall's  experiments  concerning  the  vacuous 
spots  in  the  ice. 

Those  who  have  read  his  startling  investiga- 
tions will  remember  that  by  sending  a  beam 
of  sunlight  through  ice  he  brought  to  view 
the  primitive  crystalline  forms  to  which  it 
owes  its  solidity,  and  that  he  insisted  that  these 
star-shaped  figures  are  always  in  the  plane  of 
crystallization.  Without  knowing  what  might 
be  their  origin,  I  had  myself  noticed  these  fig- 


ures, and  represented  them  in  a  diagram,  part  of 
which  is  reproduced  in  the  accompanying  wood- 


276       INTERNAL  STRUCTURE  AND 

cut.  I  had  considered  them  to  be  compressed  air- 
bubbles  ;  and  though  I  cannot,  under  my  pres- 
ent circumstances,  repeat  the  experiment  of  Dr. 
Tyndall  upon1  glacier-ice,  I  conceive  that  the  star- 
shaped  figures  represented  upon  PL  VII.  Figs. 
8  and  9,  in  my  "  Syst£me  Glaciaire,"  may  re- 
fer to  the  same  phenomenon  as  that  observed 
by  him  in  pond-ice.  Yet  while  I  make  this  con- 
cession, I  still  maintain,  that  besides  these  crys- 
talline figures  there  exist  compressed  air-bub- 
bles in  the  angular  fragments  of  the  glacier-ice, 
as  shown  in  the  preceding  wood-cut;  and  that 
these  bubbles  are  grouped  in  sets,  trending  in 
the  same  direction  in  one  and  the  same  fragment, 
and  diverging  under  various  angles  in  the  differ- 
ent fragments.  I  have  explained  this  fact  con- 
cerning the  position  of  the  compressed  air-bub- 
bles, by  assuming  that  ice,  under  various  press- 
ure, may  take  the  appearance  it  presents  in  each 
fragment  with  every  compressed  air-bubble  trend- 
ing in  the  same  direction,  while  their  diver- 
gence in  the  different  fragments  is  owing  to  a 
change  in  the  respective  position  of  the  frag- 
ments resulting  from  the  movement  of  the  whole 
glacier.  I  have  further  assumed,  that  through- 
out the  glacier  the  change  of  the  snow  and  porous 
ice  into  compact  ice  is  the  result  of  successive 
freezing,  alternating  with  melting,  or  at  least 
with  the  resumption  of  a  temperature  of  32° 


PROGRESSION   OF   GLACIERS.  277 

Fahrenheit  in  consequence  of  the  infiltration  of 
liquid  water,  to  which  the  effects  of  pressure 
must  be  added,  the  importance  of  which  in  this 
connection  no  one  could  have  anticipated  prior 
to  the  experiments  of  Dr.  Tyndall.  Of  course, 
if  the  interior  temperature  of  the  glacier  never 
falls  below  32°,  the  changes  here  alluded  to  could 
not  take  place.  But  if  the  vacuous  spaces  ob- 
served by  Dr.  Tyndall  are  really  identical  with 
the  spaces  I  have  described  as  extremely  flattened 
air-bubbles,  I  think  the  arrangement  of  these 
spaces  as  above  described  proves  that  it  freezes 
in  the  interior  of  the  glacier  to  the  depth  at 
which  these  crosswise  fragments  have  been  ob- 
served ;  that  is,  at  a  depth  of  two  hundred  feet. 
For,  since  the  experiments  of  Dr.  Tyndall  show 
that  the  vacuous  spaces  are  parallel  to  the  sur- 
face of  crystallization,  and  as  no  crystallization 
of  water  can  take  place  unless  the  surrounding 
temperature  fall  below  32°,  it  follows  that  these 
vacuous  spaces  could  not  exist  in  such  large  con- 
tinuous fragments,  presenting  throughout  the 
fragments  the  same  trend,  if  there  had  been 
no  frost  within  the  mass,  affecting  the  whole 
of  such  a  fragment  while  it  remained  in  the  same 
position. 

The  most  striking  evidence,  in  my  opinion, 
that  at  times  the  whole  mass  of  the  glacier  actu- 
ally freezes,  is  drawn  from  the  fact,  already  allu- 


278       INTERNAL  STRUCTURE  AND 

ded  to,  that,  while  the  surface  of  the  glacier  loses 
annually  from  nine  to  ten  feet  of  its  thickness  by 
evaporation  and  melting,  it  swells,  on  the  other 
hand,  in  the  spring,  to  the  amount  of  about  five 
feet.  Such  a  dilatation  can  hardly  be  the  re- 
sult of  pressure  and  the  packing  of  the  snow  and 
ice,  since  the  difference  in  the  bulk  of  the  ice 
brought  down,  during  one  year,  from  a  point 
above  to  that  under  observation,  would  not  ac- 
count for  the  swelling.  It  is  more  readily  ex- 
plained by  the  freezing  of  the  water  of  infiltration 
during  spring  and  early  summer,  when  the  in- 
filtration is  most  copious  and  the  winter  cold 
has  been  accumulating  for  the  longest  time. 
This  view  of  the  case  is  sustained  by  Elie  de 
Beaumont,  who  states  his  opinion  upon  this  point 
as  follows :  — 

"  Pendant  Thiver,  la  temperature  de  la  surface 
du  glacier  s'abaisse  a  un  grand  nombre  de  degre*s 
au-dessous  de  ze*ro,  et  cette  basse  temperature 
pe*n£tre,  quoique  avec  un  affaiblissement  graduel, 
dans  1'inte'rieur  de  la  masse.  Le  glacier  se  fen- 
dille  par  1'effet  de  la  contraction  resultant  de 
ce  refroidissement.  Les  fentes  restent  d'abord 
vides,  et  concourent  au  refroidissement  des  gla- 
ciers en  favorisant  1'introduction  de  1'air  froid  ex- 
te*rieur ;  mais  au  print emps,  lorsque  les  rayons 
du  soleil  e'chauffent  la  surface  de  la  neige  qui 
couvre  le  glacier,  ils  la  ramSnent  d'abord  a  zeYo, 


PROGRESSION  OF  GLACIERS.  279 

et  ils  produisent  ensuite  de  1'eau  &  ze*ro  qui  tombe 
dans  le  glacier  refroidi  et  fendille*.  Cette  eau  s'y 
congele  &  1'instant,  en  laissant  degager  de  la  cha- 
leur  qui  tend  a  ramener  le  glacier  a  ze*ro;  et 
le  phe*nom£ne  se  continue  jusqu'a  ce  que  la 
masse  enti£re  du  glacier  refroidi  soit  ramen^  a  la 
temperature  de  z£ro."  * 

But  where  direct  observations  are  still  so  scan- 
ty, and  the  interpretations  of  the  facts  so  con- 
flicting, it  is  the  part  of  wisdom  to  be  circum- 
spect in  forming  opinions.  This  much,  how- 
ever, I  believe  to  be  already  settled:  that  any 
theory  which  ascribes  the  very  complicated  phe- 
nomena of  the  glacier  to  one  cause  must  be  de- 
fective and  one-sided.  It  seems  to  me  most 

*"  During  the  winter,  the  temperature  at  the  surface  of 
the  glacier  sinks  a  great  many  degrees  below  32°  Fahrenheit, 
and  this  low  temperature  penetrates,  though  at  a  gradually  de- 
creasing rate,  into  the  interior  of  the  mass.  The  glacier  be- 
comes fissured  in  consequence  of  the  contraction  resulting  from 
this  cooling  process.  The  cracks  remain  open  at  first,  and  con- 
tribute to  lower  the  temperature  of  the  glacier  by  favoring 
the  introduction  of  the  cold  air  from  without ;  but  in  the  spring, 
when  the  rays  of  the  sun  raise  the  temperature  of  the  snow  cov- 
ering the  glacier,  they  first  bring  it  back  to  32°  Fahrenheit,  and 
presently  produce  water  at  32°,  which  falls  into  the  chilled 
and  fissured  mass  of  the  glacier.  There  this  water  is  instantly 
frozen,  releasing  heat  which  tends  to  bring  back  the  glacier 
to  the  temperature  of  32°;  and  this  process  continues  till  the 
entire  mass  of  the  cooled  glacier  returns  to  the  temperature 
of  32°." 


280  INTERNAL  STRUCTURE  AND 

probable,  that,  while  pressure  has  the  larger 
share  in  producing  the  onward  movement  of  the 
glacier,  as  well  as  in  the  transformation  of  the 
snow  into  ice,  a  careful  analysis  of  all  the  facts 
will  show  that  this  pressure  is  owing  partly  to 
the  weight  of  the  mass  itself,  partly  to  the  push- 
ing on  of  the  accumulated  snow  from  behind, 
partly  to  its  sliding  along  the  surface  upon  which 
it  rests,  partly  to  the  weight  of  water  pervading 
the  whole,  partly  to  the  softening  of  the  rigid 
ice  by  the  infiltration  of  water,  and  partly,  also, 
to  the  dilatation  of  the  mass,  resulting  from  the 
freezing  of  this  water.  These  causes,  of  course, 
modify  the  ice  itself,  while  they  contribute  to 
the  motion.  Further  investigations  are  required 
to  ascertain  in  what  proportion  these  different 
influences  contribute  to  the  general  result,  and 
at  what  time  and  under  what  circumstances  they 
modify  most  directly  the  motion  of  the  glacier. 

That  a  glacier  cannot  be  altogether  compared 
to  a  river,  although  there  is  an  unmistakable 
analogy  between  the  flow  of  the  one  and  the 
onward  movement  of  the  other,  seems  to  me 
plain,  —  since  the  river,  by  the  combination  of 
its  tributaries,  goes  on  increasing  in  bulk  in  con- 
sequence of  the  incompressibility  of  water,  while 
a  glacier  gradually  thins  out  in  consequence  of 
the  packing  of  its  mass,  however  large  and  nu- 
merous may  be  its  accessions.  The  analogy  fails 


PROGRESSION  OF  GLACIERS.  281 

also  in  one  important  point,  that  of  the  accelera- 
tion of  speed  with  the  steepness  of  the  slope. 
The  motion  of  the  glacier  bears  no  such  direct 
relation  to  the  inclination  of  its  bed.  And  though 
in  a  glacier,  as  in  a  river,  the  axis  of  swiftest 
motion  is  thrown  alternately  on  one  or  the  other 
side  of  the  valley,  according  to  its  shape  and 
slope,  the  very  nature  of  ice  makes  it  impossible 
that  eddies  should  be  formed  in  the  glacier,  and 
the  impressive  feature  of  whirlpools  is  altogether 
wanting  in  them.  What  have  been  called  gla- 
cier-cascades bear  only  a  remote  resemblance  to 
river-cascades,  as  in  the  former  the  surface  only 
is  thrown  into  confusion  by  breaking,  without 
affecting  the  primitive  structure ;  *  and  I  re- 
iterate my  formerly  expressed  opinion,  that  even 
the  stratification  of  the  upper  regions  is  still 
recognizable  at  the  lower  end  of  the  glacier  of 
the  Rhone. 

The  internal  structure  of  the  glacier  has  al- 
ready led  me  beyond  the  limits  I  had  proposed 
to  myself  in  the  present  article.  But  I  trust 
my  readers  will  not  be  discouraged  by  this  dry 
discussion  of  various  theories  concerning  it,  and 
will  meet  me  again  on  the  glacier,  when  we  will 
examine  together  some  of  its  more  picturesque 

*  For  the  evidence  of  this  statement  I  must,  however,  refer 
to  my  work  on  Glaciers,  already  so  often  quoted  in  this  article, 
where  it  may  be  found  with  all  the  necessary  details. 


X. 

EXTERNAL  APPEARANCE  OF  GLACIERS. 

THUS  far  we  have  examined  chiefly  the  inter- 
nal structure  of  the  glacier ;  let  us  look  now  at 
its  external  appearance,  and  at  the  variety  of  cu- 
rious phenomena  connected  with  the  deposit  of 
foreign  materials  upon  its  surface,  some  of  which 
seem  quite  inexplicable  at  first  sight.  Among 
the  most  striking  of  these  are  the  large  boulders 
elevated  on  columns  of  ice,  standing  sometimes 
ten  feet  or  more  above  the  level  of  the  glacier, 
and  the  sand-pyramids,  those  conical  hills  of 
sand  which  occur  not  infrequently  on  the  larger 
Alpine  glaciers.  One  is  at  first  quite  at  a  loss 
to  explain  the  presence  of  these  pyramids  in  the 
midst  of  a  frozen  ice-field,  and  yet  it  has  a  very 
simple  cause. 

I  have  spoken  of  the  many  little  rills  arising 
on  the  surface  of  the  ice  in  consequence  of  its 
melting.  Indeed,  the  voice  of  the  waters  is  rarely 
still  on  the  glacier  during  the  warm  season,  ex- 
cept at  night.  On  a  summer's  day,  a  thousand 
streams  are  born  before  noontide,  and  die  again 


284        EXTERNAL  APPEARANCE  OF   GLACIERS. 

at  sunset ;  it  is  no  uncommon  thing  to  see  a  full 
cascade  come  rushing  out  from  the  lower  end  of 
a  glacier  during  the  heat  of  the  day,  and  vanish 
again  at  its  decline.  Suppose  one  of  these  riv- 
ulets should  fall  into  a  deep,  circular  hole,  such 
as  often  occur  on  the  glacier,  and  the  nature  of 
which  I  shall  presently  explain,  and  that  this 
cylindrical  opening  narrows  to  a  mere  crack  at 
a  greater  or  less  depth  within  the  ice,  the  water 
will  find  its  way  through  the  crack  and  filter 
down  into  the  deeper  mass ;  but  the  dust  and 
sand  carried  along  with  it  will  be  caught  there, 
and  form  a  deposit  at  the  bottom  of  the  hole. 
As  day  after  day,  throughout  the  summer,  the 
rivulet  is  renewed,  it  carries  with  it  an  additional 
supply  of  these  light  materials,  until  the  open- 
ing is  gradually  filled  and  the  sand  is  brought 
to  a  level  with  the  surface  of  the  ice.  We  have 
already  seen,  that,  in  consequence  of  evapora- 
tion, melting,  and  other  disintegrating  causes, 
the  level  of  the  glacier  sinks  annually  at  the 
rate  of  from  five  to  ten  feet,  according  to  sta- 
tions. The  natural  consequence,  of  course,  must 
be,  that  the  sand  is  left  standing  above  the  sur- 
face of  the  ice,  forming  a  mound  which  would 
constantly  increase  in  height  in  proportion  to  the 
sinking  of  the  surrounding  ice,  had  it  sufficient 
solidity  to  retain  its  original  position.  But  a 
heap  of  sand,  if  unsupported,  must  very  soon 


EXTERNAL  APPEARANCE   OF   GLACISES.        285 

subside  and  be  dispersed ;  and,  indeed,  these 
pyramids,  which  are  often  -quite  lofty,  and  yet 
look  as  if  they  would  crumble  at  a  touch,  prove, 
on  nearer  examination,  to  be  perfectly  solid,  and 
are,  in  fact,  pyramids  of  ice  with  a  thin  sheet  of 
sand  spread  over  them.  A  word  will  explain 
how  this  transformation  is  brought  about.  As 
soon  as  the  level  of  the  glacier  falls  below  the 
sand,  thus  depriving  it  of  support,  it  sinks  down 
and  spreads  slightly  over  the  surrounding  sur- 
face. In  this  condition  it  protects  the  ice  imme- 
diately beneath  it  from  the  action  of  the  sun. 
In  proportion  as  the  glacier  wastes,  this  pro- 
tected area  rises  above  the  general  mass  and  be- 
comes detached  from  it.  The  sand,  of  course, 
slides  down  over  it,  spreading  toward  its  base, 
so  as  to  cover  a  wider  space  below,  and  an  ever- 
narrowing  one  above,  until  it  gradually  assumes 
the  pyramidal  form  in  which  we  find  it,  covered 
with  a  thin  coating  of  sand.  Every  stage  of  this 
process  may  occasionally  be  seen  upon  the  same 
glacier,  in  a  number  of  sand-piles  raised  to  va- 
rious heights  above  the  surface  of  the  ice,  ap- 
proaching the  perfect  pyramidal  form,  or  falling 
to  pieces  after  standing  for  a  short  time  erect. 

The  phenomenon  of  the  large  boulders,  sup- 
ported on  tall  pillars  of  ice,  is  of  a  similar  char- 
acter. A  mass  of  rock,  having  fallen  on  the 
surface  of  the  glacier,  protects  the  ice  immedi- 


286        EXTERNAL  APPEARANCE  OF   GLACIERS. 

ately  beneath  it  from  the  action  of  the  sun  ;  and 
as  the  level  of  the  glacier  sinks  all  around  it,  in 
consequence  of  the  unceasing  waste  of  the  sur- 
face, the  rock  is  gradually  left  standing  on  an 
ice-pillar  of  considerable  height.  In  proportion 
as  the  column  rises,  however,  the  rays  of  the  sun 
reach  its  sides,  striking  obliquely  upon  them  un- 
der the  boulder,  and  wearing  them  away,  until 
the  column  becomes  at  last  too  slight  to  sustain 
its  burden,  and  the  rock  falls  again  upon  the 
glacier ;  or,  owing  to  the  unequal  action  of  the 
sun,  striking  of  course  with  most  power  on  the 
southern  side,  the  top  of  the  pillar  becomes  slant- 
ing, and  the  boulder  slides  off.  These  ice-pillars, 
crowned  with  masses  of  rock,  form  a  very  pic- 
turesque feature  in  the  scenery  of  the  glacier, 
and  are  represented  in  many  of  the  landscapes 
in  which  Swiss  artists  have  endeavored  to  repro- 
duce the  grandeur  and  variety  of  Alpine  views, 
especially  in  the  masterly  Aquarelles  of  Lory. 
The  English  reader  will  find  them  admirably  well 
described  and  illustrated  in  Dr.  TyndalPs  work 
upon  the  glaciers.  They  are  known  throughout 
the  Alps  as  "  glacier-tables  ;  "  and  many  a  time 
my  fellow-travellers  and  I  have  spread  our  frugal 
meal  on  such  a  table,  erected,  as  it  seemed,  es- 
pecially for  our  convenience. 

Another  curious  effect  is   that  produced  by 
small  stones  or  pebbles,  small  enough  to  become 


EXTEENAL  APPEABANCE  OF  GLACIEES.        287 

heated  through  by  the  sun  in  summer.  Such  a 
heated  pebble  will  of  course  melt  the  ice  below 
it,  and  so  wear  a  hole  for  itself  into  which  it 
sinks.  This  process  will  continue  as  long  as  the 
sun  reaches  the  pebble  with  force  enough  to  heat 
it.  Numbers  of  such  deep,  round  holes,  like 
organ-pipes,  varying  in  size  from  the  diameter 
of  a  minute  pebble  or  a  grain  of  coarse  sand  to 
that  of  an  ordinary  stone,  are  found  on  the  gla- 
cier, and  at  the  bottom  of  each  is  the  pebble  by 
which  it  was  bored.  The  ice  formed  by  the  freez- 
ing of  water  collecting  in  such  holes  and  in  the 
fissures  of  the  surface  is  a  pure  crystallized  ice, 
very  different  in  color  from  the  ice  of  the  great 
mass  of  the  glacier  produced  by  snow ;  and  some- 
times, after  a  rain  and  frost,  the  surface  of  a 
glacier  looks  like  a  mosaic-work,  in  consequence 
of  such  veins  and  cylinders  or  spots  of  clear  ice 
with  which  it  is  inlaid. 

Indeed,  the  aspect  of  the  glacier  changes  con- 
stantly with  the  different  conditions  of  the  tem- 
perature. We  may  see  it,  when,  during  a  long 
dry  season,  it  has  collected  upon  its  surface  all 
sorts  of  light  floating  materials,  as  dust,  sand, 
and  the  like,  so  that  it  looks  dull  and  soiled, — 
or  when  a  heavy  rain  has  washed  the  surface 
clean  from  all  impurities  and  left  it  bright  and 
fresh.  We  may  see  it  when  the  heat  and  other 
disintegrating  influences  have  acted  upon  the  ice 


288        EXTERNAL  APPEARANCE  OF   GLACIERS. 

to  a  certain  superficial  depth,  so  that  its  surface 
is  covered  with  a  decomposed  crust  of  broken, 
snowy  ice,  so  permeated  with  air  that  it  has 
a  dead-white  color,  like  pounded  ice  or  glass. 
Those  who  see  the  glacier  in  this  state  miss  the 
blue  tint  so  often  described  as  characteristic  of 
its  appearance  in  its  lower  portion,  and  as  giving 
such  a  peculiar  beauty  to  its  caverns  and  vaults. 
But  let  them  come  again  after  a  summer  storm 
has  swept  away  this  loose  sheet  of  broken,  snowy 
ice  above,  and  before  the  same  process  has  had 
time  to  renew  it,  and  they  will  find  the  compact, 
solid  surface  of  the  glacier  of  as  pure  a  blue  as 
if  it  reflected  the  sky  above.  We  may  see  it  in 
the  early  dawn,  before  the  new  ice  of  the  preced- 
ing night  begins  to  yield  to  the  action  of  the  sun, 
and  the  surface  of  the  glacier  is  veined  and  in- 
laid with  the  water  poured  into  its  holes  and  fis- 
sures during  the  day,  and  transformed  into  pure, 
fresh  ice  during  the  night,  —  or  when  the  noon- 
day heat  has  wakened  all  its  streams,  and  rivu- 
lets sometimes  as  large  as  rivers  rush  along  its 
surface,  find  their  way  to  the  lower  extremity 
of  the  glacier,  or,  dashing  down  some  gaping 
crevasse  or  open  well,  are  lost  beneath  the  ice. 

It  would  seem,  from  the  quantity  of  water  that 
is  sometimes  ingulfed  within  these  open  breaks 
in  the  ice,  that  the  glacier  must  occasionally  be 
fissured  to  a  very  great  depth.  I  remember  once, 


EXTERNAL  APPEARANCE   OF   GLACIERS.        289 

when  boring  a  hole  in  the  glacier  in  order  to  let 
down  a  self-regulating  thermometer  into  its  in- 
terior, seeing  an  immense  fissure  suddenly  rent 
open,  in  consequence,  no  doubt,  of  the  shocks 
given  to  the  ice  by  the  blows  of  the  instruments. 
The  effect  was  like  that  of  an  earthquake  ;  the 
mass  seemed  to  rock  beneath  us,  and  it  was  dif- 
ficult to  keep  our  feet.  One  of  these  glacial 
rivers  was  flowing  past  the  spot  at  the  time,  and 
it  was  instantly  lost  in  the  newly  formed  chasm. 
However  deep  and  wide  the  fissure  might  be, 
such  a  stream  of  water,  constantly  poured  into 
it,  and  daily  renewed  throughout  the  summer, 
must  eventually  fill  it  and  overflow,  unless  it 
finds  its  way  through  the  whole  mass  of  the  gla- 
cier to  the  bottom  on  which  it  rests ;  —  it  must 
have  an  outlet  above  or  below.  The  fact  that 
considerable  rivulets  (too  broad  to  leap  across, 
and  too  deep  to  wade  through  safely  even  with 
high  boots)  may  entirely  vanish  in  the  glacier 
unquestionably  shows  one  of  two  things,  —  that 
the  whole  mass  must  be  soaked  with  water  like 
a  wet  sponge,  or  the  cavities  must  reach  the  bot- 
tom of  the  glacier.  Probably  the  two  conditions 
are  generally  combined. 

In  direct  connection  with  the  narrower  fissures 
are  the  so-called  moulins,  —  the  circular  wells  on 
the  glacier  already  alluded  to  when  speaking  of 
the  sand-hills.  We  will  suppose  that  a  trans- 

13  S 


290        EXTERNAL  APPEARANCE  OF   GLACIERS. 

verse,  narrow  fissure  has  been  formed  across  the 
glacier,  and  that  one  of  the  many  rivulets  flow- 
ing longitudinally  along  its  surface  empties  into 
it.  As  the  surface-water  of  the  glacier  produc- 
ing these  rivulets  arises  not  only  from  the  melt- 
ing of  the  ice  but  also  from  the  condensation  of 
vapor,  or  even  from  rain-falls,  and  flows  over  the 
scattered  dust-particles  and  fragments  of  rock,  it 
has  always  a  temperature  slightly  above  32°,  so 
that  such  a  rivulet  is  necessarily  warmer  than 
the  icy  edge  of  the  fissure  over  which  it  precip- 
itates itself.  In  consequence  of  its  higher  tem- 
perature it  melts  the  edge,  gradually  wearing  it 
backward,  till  the  straight  margin  of  the  fissure 
at  the  spot  over  which  the  water  falls  is  changed 
;to  a  semicircle  ;  and,  as  much  of  the  water  dashes 
in  spray  and  foam  against  the  other  side,  the  same 
effect  takes  place  there,  by  which  a  corresponding 
semicircle  is  formed  exactly  opposite  the  first. 
This  goes  on  not  only  at  the  upper  margin,  but 
through  the  whole  depth  of  the  opening  as  far 
down  as  the  water  carries  its  higher  tempera- 
ture. In  short,  a  semicircular  groove  is  exca- 
vated on  either  side  of  the  fissure  for  its  whole 
depth  along  the  line  on  which  the  rivulet  holds 
its  downward  course.  After  a  time,  in  conse- 
quence of  the  motion  of  the  glacier,  such  a  fis- 
sure may  close  again,  and  then  the  two  semicir- 
cles thus  brought  together  form  at  once  one 


EXTERNAL   APPEARANCE   OF   GLACIERS.        291 

continuous  circle,  and  we  have  one  of  the  round 
deep  openings  on  the  glacier  known  as  moulins, 
or  wells,  which  may  of  course  become  perfectly 
dry  if  any  accident  turns  the  rivulet  aside  or 
dries  up  its  source.  The  most  common  cause  of 
the  intermittence  of  such  a  waterfall  is  the  for- 
mation of  a  crevasse  higher  up,  across  the  water 
course  which  supplied  it,  and  which  now  begins 
another  excavation. 

These  wells  are  often  very  profound.  I  have 
lowered  a  line  for  more  than  seven  hundred  feet 
in  one  of  them  before  striking  bottom  ;  and  one 
is  by  no  means  sure  even  then  of  having  sounded 
the  whole  depth,  for  it  may  often  happen  that 
the  water  meets  with  some  obstacle  which  pre- 
vents its  direct  descent,  and,  turning  aside,  con- 
tinues its  deeper  course  at  a  different  angle. 
Such  a  well  may  be  like  a  crooked  shaft  in  a 
mine,  changing  its  direction  from  time  to  time. 
I  found  this  to  be  the  case  in  one  into  which  I 
caused  myself  to  be  lowered  in  order  to  examine 
the  internal  structure  of  the  glacier.  For  some 
time  my  descent  was  straight  and  direct,  but  at 
a  depth  of  about  fifty  feet  there  was  a  landing- 
place,  as  it  were,  from  which  the  opening  con- 
tinued its  farther  course  at  quite  a  different  an- 
gle. It  is  within  these  cylindrical  openings  in 
the  ice  that  those  accumulations  of  sand  collect 
which  form  the  pyramids  described  above. 


292       EXTERNAL  APPEARANCE  OF   GLACIERS. 

One  may  often  trace  the  gradual  formation  of 
these  wells,  because,  as  they  require  certain  sim- 
ilar conditions,  they  are  very  apt  to  be  found  in 
various  stages  of  completion  along  the  same  track 
where  these,  conditions  occur.  Fissures,  for  in- 
stance, will  often  be  produced  along  the  same 
line,  because,  as  the  mass  of  the  glacier  moves 
on,  its  upper  portions,  as  they  advance,  come 
successively  in  contact  with  inequalities  of  the 
bottom,  in  consequence  of  which  the  ice  is 
strained  beyond  its  power  of  resistance  and 
cracks  across.  Rivulets  are  also  likely  to  be 
renewed  summer  after  summer  over  the  same 
track,  because  certain  conditions  of  the  surface 
of  the  glacier,  to  which  I  have  not  yet  alluded, 
and  which  favor  the  more  rapid  melting  of 
the  ice,  remain  unchanged  year  after  year.  Of 
course,  the  wells  do  not  remain  stationary  any 
more  than  any  other  feature  of  the  glacier* 
They  move  on  with  the  advancing  mass  of  ice, 
and  we  consequently  find  the  older  ones  consid- 
erably lower  down  than  the  more  recent  ones. 
In  ascending  such  a  track  as  I  have  described, 
along  which  fissures  and  rivulets  are  likely  to 
occur,  we  may  meet  first  with  a  sand-pyramid ; 
at  a  certain  distance  above  that  there  may  be  a 
circular  opening  filled  to  its  brim  with  the  sand 
which  has  just  reached  the  surface  of  the  ice  ;  a 
little  above  may  be  an  open  well  with  the  rivulet 


EXTERNAL  APPEARANCE   OF   GLACIERS.        293 

still  pouring  into  it ;  or,  higher  up,  we  may  meet 
an  open  fissure  with  the  two  semicircles  opposite 
each  other  on  the  margins,  but  not  yet  united, 
as  they  will  be  presently  by  the  closing  of  the 
fissure  ;  or  we  may  find  near  by  another  fissure, 
the  edges  of  which  are  just  beginning  to  wear  in 
consequence  of  the  action  of  the  water.  Thus, 
though  we  cannot  trace  the  formation  of  such  a 
cylindrical  shaft  in  the  glacier  from  the  begin- 
ning to  the  end,  we  may,  by  combining  the  sep- 
arate facts  observed  in  a  number,  decipher  their 
whole  history. 

In  describing  the  surface  of  the  glacier,  I 
should  not  omit  the  shallow  troughs,  which  I 
have  called  "  meridian  holes,"  from  the  accu- 
racy with  which  they  register  the  position  of 
the  sun.  Here  and  there  on  the  glacier  there 
are  patches  of  loose  materials,  dust,  sand,  peb- 
bles, or  gravel,  accumulated  by  diminutive  water- 
rills,  and  small  enough  to  become  heated  during 
the  day.  They  will,  of  course,  be  warmed  first 
on  their  eastern  side,  then,  still  more  powerfully, 
on  their  southern  side,  and  in  the  afternoon  with 
less  force  again  on  their  western  side,  while  the 
northern  side  will  remain  comparatively  cool. 
Thus  around  more  than  half  of  their  circumfer- 
ence they  melt  the  ice  in  a  semicircle,  and  the 
glacier  is  covered  with  little  crescent-shaped 
troughs  of  this  description,  with  a  steep  wall  on 


294       EXTERNAL  APPEARANCE   OF   GLACIERS. 

one  side  and  a  shallow  one  on  the  other,  and  a 
little  heap  of  loose  materials  in  the  bottom. 
They  are  the  sun-dials  of  the  glacier,  recording 
the  hour  by  the  advance  of  the  sun's  rays  upon 
them. 

In  recapitulating  the  results  of  my  glacial  ex- 
perience, even  in  so  condensed  a  form  as  that  in 
which  I  intend  to  present  them  here,  I  shall  be 
obliged  to  enter  somewhat  into  personal  narra- 
tion, though  at  the  risk  of  repeating  what  has 
been  already  told  by  the  companions  of  my  ex- 
cursions, some  of  whom  wrote  out  in  a  more  pop- 
ular form  the  incidents  of  our  daily  life  which 
could  not  be  fitly  introduced  into  my  own  record 
of  scientific  research.  When  I  first  began  my 
investigations  upon  the  glaciers,  now  more  than 
twenty-five  years  ago,  scarcely  any  measurements 
of  their  size  or  their  motion  had  been  made.  One 
of  my  principal  objects,  therefore,  was  to  ascer- 
tain the  thickness  of  the  mass  of  ice,  generally 
supposed  to  be  from  eighty  to  a  hundred  feet, 
and  even  less.  The  first  year  I  took  with  me  a 
hundred  feet  of  iron  rods,  (no  easy  matter,  where 
it  had  to  be  transported  to  the  upper  part  of  a 
glacier  on  men's  backs,)  thinking  to  bore  the 
glacier  through  and  through.  As  well  might  I 
have  tried  to  sound  the  ocean  with  a  ten-fathom 
line.  The  following  year  I  took  two  hundred 


EXTEKNAL  APPEARANCE   OF   GLACIERS.        295 

feet  of  rods  with  me,  and  again  I  was  foiled. 
Eventually  I  succeeded  in  carrying  up  a  thou- 
sand feet  of  line,  and  satisfied  myself,  after  many 
attempts,  that  this  was  about  the  average  thick- 
ness of  the  glacier  of  the  Aar,  on  which  I  was 
working. 

I  mention  these  failures,  because  they  give 
some  idea  of  the  discouragements  and  difficulties 
which  meet  the  investigator  in  any  new  field  of 
research ;  and  the  student  must  remember,  for 
his  consolation  under  such  disappointments,  that 
his  failures  are  almost  as  important  to  the  cause 
of  science  and  to  those  who  follow  him  in  the 
same  road  as  his  successes.  It  is  much  to  know 
what  we  cannot  do  in  any  given  direction,  —  the 
first  step,  indeed,  toward  the  accomplishment  of 
what  we  can  do. 

A  like  disappointment  awaited  me  in  my  first 
attempt  to  ascertain  by  direct  measurement  the 
rate  of  motion  in  the  glacier.  Early  observers 
had  asserted  that  the  glacier  moved,  but  there 
had  been  no  accurate  demonstration  of  the  fact, 
and  so  uniform  is  its  general  appearance  from 
year  to  year  that  even  the  fact  of  its  motion  was 
denied  by  many.  It  is  true  that  the  progress 
of  boulders  had  been  watched ;  a  mass  of  rock 
which  had  stood  at  a  certain  point  on  the  glacier 
was  found  many  feet  below  that  point  the  follow- 
ing year ;  but  the  opponents  of  the  theory  insisted 


296       EXTERNAL  APPEARANCE   OF   GLACIERS. 

that  it  did  not  follow,  because  the  mass  of  rock 
had  moved,  that  therefore  the  mass  of  ice  had 
moved  with  it.  They  believed  that  the  boulder 
might  have  slid  down  for  that  distance.  Neither 
did  the  occasional  encroachment  of  the  glaciers 
upon  the  valleys  prove  anything ;  it  might  be 
solely  the  effect  of  an  unusual  accumulation  of 
snow  in  cold  seasons.  Here,  then,  was  another 
question  to  be  tested ;  and  one  of  my  first  ex- 
periments was  to  plant  stakes  in  the  ice  to  ascer- 
tain whether  they  would  change  their  position 
with  reference  to  the  sides  of  the  valley  or  not. 
If  the  glacier  moved,  my  stake  must  of  course 
move  with  it;  if  it  was  stationary,  my  stakes 
would  remain  standing  where  I  had  placed  them, 
and  any  advance  of  other  objects  upon  the  surface 
of  the  glacier  would  be  proved  to  be  due  to  their 
sliding,  or  to  some  motion  of  their  own,  and  not 
to  that  of  the  mass  of  ice  on  which  they  rested. 
I  found  neither  the  one  nor  the  other  of  my 
anticipated  results ;  after  a  short  time,  all  the 
stakes  lay  flat  on  the  ice,  and  I  learned  nothing 
from  my  first  series  of  experiments,  except  that 
the  surface  of  the  glacier  is  wasted  annually  for 
a  depth  of  at  least  five  feet,  in  consequence  of 
which  my  rods  had  lost  their  support,  and  fallen 
down.  Similar  disappointment  was  experienced 
by  my  friend  Escher  upon  the  great  glacier  of 
Aletsch. 


EXTERNAL  APPEARANCE   OF   GLACIERS.        297 

My  failure,  however,  taught  me  to  sink  the 
next  set  of  stakes  ten  or  fifteen  feet  below  the 
surface  of  the  ice,  instead  of  five ;  and  the  ex- 
periment was  attended  with  happier  results.  A 
stake  planted  eighteen  feet  deep  in  the  ice,  and 
cut  on  a  level  with  the  surface  of  the  glacier, 
in  the  summer  of  1840,  was  found,  on  my  return 
in  the  summer  of  1841,  to  project  seven  feet, 
and  in  the  beginning  of  September  it  showed 
ten  feet  above  the  surface.  Before  leaving  the 
glacier,  in  September,  1841, 1  planted  six  stakes, 
at  a  certain  distance  from  each  other,  in  a  straight 
line  across  the  upper  part  of  the  glacier,  taking 
care  to  have  the  position  of  all  the  stakes  deter- 
mined with  reference  to  certain  fixed  points  on 
the  rocky  walls  of  the  valley.  When  I  returned, 
the  following  year,  all  the  stakes  had  advanced 
considerably,  and  the  straight  line  had  changed 
to  a  crescent,  the  central  rods  having  moved 
forward  much  faster  than  those  nearer  the  sides, 
so  that  not  only  was  the  advance  of  the  glacier 
clearly  demonstrated,  but  also  the  fact  that  its 
middle  portion  moved  faster  than  its  margins. 
This  furnished  the  first  accurate  data  on  record 
concerning  the  average  movement  of  the  glacier 
during  the  greater  part  of  one  year.  In  1842 
I  caused  a  trigonometric  survey  of  the  whole 
glacier  of  the  Aar  to  be  made,  and  several  lines 
across  its  whole  width  were  staked  and  deter- 

13* 


298        EXTERNAL  APPEARANCE   OF   GLACIERS. 

mined  with  reference  to  the  sides  of  the  valley ;  * 
for  a  number  of  successive  years  the  survey 
was  repeated,  and  furnished  the  numerous  data 
concerning  the  motion  of  the  glacier  which  I 
have  published.  I  shall  probably  never  have  an 
opportunity  of  repeating  these  experiments,  and 
examining  anew  the  condition  of  the  glacier  of 
the  Aar ;  but,  as  all  the  measurements  were  taken 
with  reference  to  certain  fixed  points  recorded 
upon  the  map  mentioned  in  the  note,  it  would 
be  easy  to  renew  them  over  the  same  locality, 
and  to  make  a  direct  comparison  with  my  first 
results  after  an  interval  of  a  quarter  of  a  century. 
Such  a  comparison  would  be  very  valuable  to 
science,  as  showing  any  change  in  the  condition 
of  the  glacier,  its  rate  of  motion,  etc.,  since  the 
tune  my  survey  was  made. 

These  observations  not  only  determined  the 
fact  of  the  motion  of  the  glacier  itself,  as  well 
as  the  inequality  of  its  motion  in  different  parts, 
but  explained  also  a  variety  of  phenomena  in- 
directly connected  with  it.  Among  these  were 
the  position  and  direction  of  the  crevasses,  those 
gaping  fissures  of  unknown  depths,  sometimes 

*  All  the  trigonometrical  measurements  connected  with  my 
experiments  were  very  ably  conducted  by  Mr.  Wild,  now  Pro- 
fessor at  the  Federal  Polytechnic  School  in  Zurich;  they  are 
recorded  in  the  topographical  survey  and  map  of  the  glacier 
of  the  Aar,  accompanying  my  "  Systeme  Glaciaire." 


EXTERNAL  APPEARANCE   OF   GLACIERS.        299 

a  mile  or  more  in  length,  and  often  measuring 
several  hundred  feet  in  width,  the  terror,  not 
only  of  the  ordinary  traveller,  but  of  the  most 
experienced  mountaineers.  There  is  a  variety 
of  such  crevasses  upon  the  glacier,  but  the  most 
numerous  and  dangerous  are  the  transverse  and 
lateral  ones.  The  transverse  ones  were  readily 
accounted  for  after  the  motion  of  the  glacier 
was  admitted ;  they  must  take  place,  whenever, 
in  consequence  of  the  advance  of  the  glacier 
over  inequalities  or  steeper  parts  of  its  bed,  the 
tension  of  the  mass  was  so  great  that  the  cohe- 
sion of  the  particles  was  overcome,  and  the  ice 
consequently  rent  apart.  This  would  be  espe- 
cially the  case  wherever  some  steep  angle  in 
the  bottom  over  which  it  moved  presented  an 
obstacle  to  the  even  advance  of  the  mass.  But 
the  position  of  the  lateral  ones  was  not  so  easily 
understood.  They  are  especially  apt  to  occur 
wherever  a  promontory  of  rock  juts  out  into 
the  glacier ;  and,  when  fresh,  they  usually  slant 
obliquely  upward,  trending  from  the  prominent 
wall  toward  the  head  of  the  glacier,  while,  when 
old,  on  the  contrary,  they  turn  downward,  so 
that  the  crevasses  around  such  a  promontory  are 
often  arranged  in  the  shape  of  a  spread  fan, 
diverging  from  it  in  different  directions.  When 
the  movement  of  the  glacier  was  fully  under- 
stood, however,  it  became  evident,  that,  in  its 


300       EXTERNAL  APPEARANCE   OF   GLACIERS. 

effort  to  force  itself  around  the  promontory,  the 
ice  was  violently  torn  apart,  and  that  the  rent 
must  take  place  in  a  direction  at  right  angles 
with  that  in  which  the  mass  was  moving.  If 
the  mass  be  moving  inward  and  downward,  the 
direction  of  the  rent  must  be  obliquely  upward. 
As  now  the  mass  continues  to  advance,  the  cre- 
vasses must  advance  with  it ;  and,  as  it  .moves 
more  rapidly  toward  the  middle  than  on  the  mar- 
gins, that  end  of  the  crevasse  which  is  farthest 
removed  from  the  projecting  rock  must  move 
more  rapidly  also ;  the  consequence  is,  that  all 
the  older  lateral  crevasses,  after  a  certain  time, 
point  downward,  while  the  fresh  ones  point  up- 
ward. 

Not  only  does  the  glacier  collect  a  variety  of 
foreign  materials  on  its  upper  surface,  but  its 
sides  as  well  as  its  lower  surface  are  studded 
with  boulders,  stones,  pebbles,  sand,  coarse  and 
fine  gravel,  so  that  it  forms  in  reality  a  gigantic 
rasp,  with  sides  hundreds  of  feet  deep,  and  a 
surface  thousands  of  feet  wide  and  many  miles  in 
length,  grinding  over  the  bottom  and  along  the 
walls  between  which  it  moves,  polishing,  grooving, 
and  scratching  them  as  it  passes  onward.  One 
who  is  familiar  with  the  track  of  this  mighty 
engine  will  recognize  at  once  where  the  large 
boulders  have  hollowed  out  their  deeper  furrows, 
where  small  pebbles  have  drawn  their  finer  marks, 


EXTERNAL  APPEARANCE  OF   GLACIERS.        301 

where  the  stones  with  angular  edges  have  left 
their  sharp  scratches,  where  sand  and  gravel  have 
rubbed  and  smoothed  the  rocky  surface,  and  left 
it  bright  and  polished  as  if  it  came  from  the 
hand  of  the  marble-worker.  These  marks  are 
not  to  be  mistaken  by  any  one  who  has  carefully 
observed  them ;  the  scratches,  furrows,  grooves, 
are  always  rectilinear,  trending  in  the  direction 
in  which  the  glacier  is  moving,  and  most  distinct 
on  that  side  of  the  surface-inequalities  facing  the 
direction  of  the  moving  mass,  while  the  lee-side 
remains  mostly  untouched. 

It  may  be  asked,  how  it  is  known  that  the  gla- 
cier carries  this  powerful  apparatus  on  its  sides 
and  bottom,  when  they  are  hidden  from  sight. 
I  answer,  that  we  might  determine  the  fact  theo- 
retically from  certain  known  conditions  respecting 
the  conformation  of  the  glacier,  to  which  I  shall 
allude  presently ;  but  we  need  not  resort  to  this 
kind  of  evidence,  since  we  have  ocular  demon- 
stration of  the  truth.  Here  and  there  on  the 
sides  of  the  glacier  it  is  possible  to  penetrate 
between  the  walls  and  the  ice  to  a  great  depth, 
and  even  to  follow  such  a  gap  to  the  very  bottom 
of  the  valley ;  and  everywhere  do  we  find  the 
surface  of  the  ice  fretted,  as  I  have  described  it, 
with  stones  of  every  size,  from  the  pebble  to  the 
boulder,  and  also  with  sand  and  gravel  of  all 
sorts,  from  the  coarsest  grain  to  the  finest ;  and 


302       EXTERNAL  APPEARANCE   OF  GLACIERS. 

these  materials,  more  or  less  firmly  set  in  the 
ice,  form  the  grating  surface  with  which,  in  its 
onward  movement  down  the  Alpine  valleys,  it 
leaves  everywhere  unmistakable  traces  of  its  pas- 
sage. 

We  come  now  to  the  moraines,  those  walls  of 
loose  materials  built  by  the  glaciers  themselves 
along  their  road.  They  have  been  divided  into 
three  classes,  namely,  lateral,  medial,  and  ter- 
minal moraines.  Let  us  look  first  at  the  lateral 
ones  ;  and  to  understand  them  we  must  examine 
the  conformation  of  the  glacier  below  the  neve*, 
where  it  assumes  the  character  of  pure  compact 
ice.  We  have  seen  that  the  fields  of  snow,  where 
the  glaciers  have  their  origin,  are  level,  and  that 
lower  down,  where  these  masses  of  snow  begin 
to  descend  toward  the  narrower  valley,  they  fol- 
low its  trough-like  shape,  sinking  toward  the 
centre  and  sloping  upward  against  the  sides,  so 
that  the  surface  of  the  glacier,  about  the  region 
of  the  neve,  is  slightly  concave.  But  lower  down 
in  the  glacier  proper,  where  it  is  completely 
transformed  into  ice,  its  surface  becomes  convex, 
for  the  following  reason.  The  rocky  walls  of 
the  valley,  as  they  approach  the  plain,  partake 
of  its  high  temperature.  They  become  heated 
by  the  sun  during  the  day  in  summer,  so  that 
the  margins  of  the  glacier  melt  rapidly  in  contact 
with  them.  In  consequence  of  this,  there  is 


EXTERNAL   APPEAEANCE   OF   GLACIERS.        303 

always  in  the  lower  part  of  the  glacier  a  broad 
depression  between  the  ice  and  the  rocky  walls, 
while,  as  this  effect  is  not  felt  in  the  centre  of 
the  glacier,  it  there  retains  a  higher  level.  The 
natural  result  of  this  is  a  convex  surface,  arching 
upward  toward  the  middle,  sinking  toward  the 
sides.  It  is  in  these  broad,  marginal  depressions 
that  the  lateral  moraines  accumulate ;  masses  of 
rock,  stones,  pebbles,  dust,  all  the  fragments,  in 
short,  which  become  loosened  from  the  rocky 
walls  above,  fall  into  them,  and  it  is  a  part  of 
the  materials  so  accumulated  which  gradually 
work  their  way  downward  between  the  ice  and 
the  walls,  till  the  whole  side  of  the  glacier  be- 
comes studded  with  them.  It  is  evident,  that, 
when  the  glacier  runs  in  a  northerly  or  southerly 
direction,  both  the  walls  will  be  affected^  by  the 
sun,  one  in  the  morning,  the  other  in  the  after- 
noon, and  in  such  a  case  the  sides  will  be  uni- 
form, or  nearly  so.  But  when  the  trend  of  the 
valley  is  from  east  to  west,  or  from  west  to  east, 
the  northern  side  only  will  feel  the  full  force  of 
the  sun;  and  in  such  a  case,  only  one  side  of 
the  glacier  will  be  convex  in  outline,  while  the 
other  will  remain  nearly  on  a  level  with  the  mid- 
dle. The  large  masses  of  loose  materials  which 
accumulate  between  the  glacier  and  its  rocky 
walls  and  upon  its  margins  form  the  lateral  mo- 
raines. These  move  most  slowly,  as  the  marginal 


304       EXTERNAL  APPEARANCE   OF   GLACIERS. 

portions  of  the  glacier  advance  at  a  much  slower 
rate  than  its  centre. 

The  medial  moraines  arise  in  a  different  way, 
though  they  are  directly  connected  with  the  lat- 
eral moraines.  It  often  happens  that  two  smaller 
glaciers  unite,  running  into  each  other  to  form 
a  larger  one.  Suppose  two  glaciers  to  be  moving 
along  two  adjoining  valleys,  converging  toward 
each  other,  and  running  in  an  easterly  or  westerly 
direction ;  at  a  certain  point  these  two  valleys 
open  into  a  single  valley,  and  here,  of  course, 
the  two  glaciers  must  meet,  like  two  rivers  rush- 
ing into  a  common  bed.  But  as  glaciers  consist 
of  a  solid,  and  not  a  fluid,  there  will  be  no  in- 
discriminate mingling  of  the  two,  and  they  will 
hold  their  course  side  by  side.  This  being  the 
case,  the  lateral  moraine  on  the  southern  side  of 
the  northernmost  glacier,  and  that  on  the  northern 
side  of  the  southernmost  one,  must  meet  in  the 
centre  of  the  combined  glaciers.  Such  are  the 
so-called  medial  moraines  formed  by  the  junction 
of  two  lateral  ones.  Sometimes  a  glacier  may 
have  a  great  number  of  tributaries,  and  in  that 
case  we  may  see  several  such  moraines  running 
in  straight  lines  along  its  surface,  all  of  which  are 
called  medial  moraines  in  consequence  of  their 
origin  midway  between  two  combining  glaciers. 
The  glacier  of  the  Aar,  represented  in  the  wood- 
cut opposite,  affords  a  striking  example  of  a  large 


EXTERNAL   APPEARANCE   OF   GLACIERS.        305 


NOTE.  —  The  cuts  on  pp.  305  and  307  have  accidentally  been 
reversed,  —  what  is  on  the  left  should  be  on  the  right,  and  rice 
versa ;  they  must  therefore  be  considered  only  as  diagrams  of  a 
junction  of  two  glaciers  and  of  a  terminal  moraine. 


306       EXTERNAL  APPEARANCE   OF   GLACIERS. 

medial  moraine.  It  is  formed  by  the  junction 
of  the  glaciers  of  the  Lauter-Aar,  on  the  right- 
hand  side  of  the  wood-cut,  and  the  Finster-Aar, 
on  the  left ;  and  the  union  of  their  inner  lateral 
moraines,  in  the  centre  of  the  diagram,  forms 
the  stony  wall  down  the  centre  of  the  larger 
glacier,  called  its  medial  moraine.  This  moraine 
at  some  points  is  not  less  than  sixty  feet  high. 
We  have  here  an  effect  similar  to  that  of  the 
glacier-tables  and  the  sand-pyramids.  The  wall 
protects  the  ice  beneath  it,  and  prevents  it  from 
sinking  at  the  same  rate  as  the  surrounding  sur- 
face, while  its  heated  surface  increases  the  melt- 
ing of  the  adjacent  surfaces  of  ice,  thus  forming 
longitudinal  depressions  along  the  medial  mo- 
raines, in  which  the  largest  rivulets  and  the  most 
conspicuous  sand-pyramids,  the  deepest  wells  and 
the  finest  waterfalls,  are  usually  met 'with.  As 
the  medial  moraines  rest  upon  that  part  of  the 
glacier  which  moves  fastest,  they  of  course  ad- 
vance much  more  rapidly  than  the  lateral  mo- 
raines. 

The  terminal  moraines  consist  of  all  the  debris 
brought  down  by  the  glacier  to  its  lower  extrem- 
ity. In  consequence  of  the  more  rapid  movement 
of  the  centre  of  the  glacier,  it  always  terminates 
in  a  semicircle  at  its  lower  end,  where  these 
materials  collect,  and  the  terminal  moraines,  of 
course,  follow  the  outline  of  the  glacier.  The 


EXTERNAL  APPEARANCE   OF   GLACIERS.        307 

wood-cut  below  represents  the  terminal  moraine 
of  the  glacier  of  Yiesch. 


Sometimes,  when  a  number  of  cold  summers 
have  succeeded  each  other,  preventing  the  glacier 
from  melting  in  proportion  to  its  advance,  the  ac- 


308        EXTERNAL  APPEARANCE  OF  GLACIERS. 

cumulation  of  materials  at  its  terminus  becomes 
very  considerable ;  and  when,  in  consequence  of 
a  succession  of  warm  summers,  it  gradually  melts 
and  retreats  from  the  line  it  has  been  occupying, 
a  large  semicircular  wall  is  left,  spanning  the  val- 
ley from  side  to  side,  through  which  the  stream 
issuing  from  the  glacier  may  be  seen  cutting 
its  way.  It  is  important  to  notice  that  such 
terminal  moraines  may  actually  span  the  whole 
width  of  a  valley,  from  side  to  side,  and  be  in- 
terrupted only  where  watercourses  of  sufficient 
power  break  through  them.  To  suppose  that 
such  transverse  walls  of  loose  materials  could 
be  thrown  across  a  valley  by  a  river  were  to  sup- 
pose that  it  could  build  dams  across  its  bed  while 
it  is  flowing.  Such  transverse  or  crescent-shaped 
moraines  are  everywhere  the  work  of  glaciers. 

All  these  moraines  are  the  landmarks,  so  to 
speak,  by  which  we  trace  the  height  and  extent, 
as  well  as  the  progress  and  retreat,  of  glaciers 
in  former  times.  Suppose,  for  instance,  that  a 
glacier  were  to  disappear  entirely.  For  ages  it- 
has  been  a  gigantic  ice-raft,  receiving  all  sorts 
of  materials  on  its  surface  as  it  travelled  onward, 
and  bearing  them  along  with  it ;  while  the  hard 
particles  of  rock  set  in  its  lower  surface  have 
been  polishing  and  fashioning  the  whole  surface 
over  which  it  extended.  As  it  now  melts,  it  drops 
its  various  burdens  on  the  ground ;  boulders  are 


EXTERNAL  APPEARANCE   OF  GLACIERS.        309 

the  milestones  marking  the  different  stages  of 
its  journey,  the  terminal  and  lateral  moraines 
are  the  framework  which  it  erected  around  itself 
as  it  moved  forward,  and  which  define  its  boun- 
daries centuries  after  it  has  vanished,  while  the 
scratches  and  furrows  it  has  left  on  the  surface 
below  show  the  direction  of  its  motion. 

All  the  materials  which  reach  the  bottom  of 
the  glacier,  and  are  moving  under  its  weight, 
so  far  as  they  are  not  firmly  set  in  the  ice,  must 
be  pressed  against  one  another,  as  well  as  against 
the  rocky  bottom,  and  will  be  rounded  off,  pol- 
ished, and  scratched,  like  the  rock  itself  over 
which  they  pass.  The  pebbles  or  stones  set  fast 
in  the  ice  will  be  thus  polished  and  scratched, 
however,  only  over  the  surface  exposed ;  but,  as 
they  may  sometimes  move  in  their  socket,  like 
a  loosely  mounted  stone,  the  different  surfaces 
may  in  turn  undergo  this  process,  and  in  the 
end  all  the  loose  materials  under  a  glacier  become 
more  or  less  polished,  scratched,  and  grooved. 
These  marks  exhibit  also  the  peculiarity  so  char- 
acteristic of  the  grooves  and  scratches  on  the 
bed  and  walls  of  the  valley  ;  they  are  rectilinear, 
trending  in  the  direction  in  which  the  superin- 
cumbent mass  advances,  though,  of  course,  owing 
to  the  changes  in  the  position  of  the  pebbles  or 
boulders,  they  may  cross  each  other  in  every 
direction  on  their  surface. 


310       EXTERNAL  APPEARANCE   OF   GLACIERS. 

As  the  large  materials  are  pressed  onward  with 
the  finer  ones,  that  is,  with  the  sand,  gravel,  and 
mud  accumulated  at  the  bottom  of  the  glacier, 
the  component  parts  of  this  underlying  bed  of 
debris  will  be  mixed  together  without  any  refer- 
ence to  their  size  or  weight.  The  softest  mud 
and  finest  sand  may  be  in  immediate  contact 
with  the  bottom  of  the  valley,  while  larger  rocks 
and  pebbles  may  be  held  in  the  ice  above ;  or 
their  position  may  be  reversed,  and  the  coarser 
materials  may  rest  below,  while  the  finer  ones 
are  pressed  between  them  or  overlying  them. 
In  short,  the  whole  accumulation  of  loose  debris 
under  the  glacier,  resulting  from  the  trituration 
of  all  kinds  of  angular  fragments  reaching  the 
lower  surface  of  the  ice,  presents  a  sort  of  paste, 
in  which  coarser  and  lighter  materials  are  im- 
pacted without  reference  to  bulk  or  weight.  Those 
fragments  which  are  most  polished,  rounded, 
grooved,  or  scratched,  have  travelled  longest 
under  the  glacier,  and  are  derived  from  the  hard- 
est rocks,  which  have  resisted  the  general  crush- 
ing and  pounding  for  a  longer  time.  The  masses 
of  rock  on  the  upper  surface  of  the  glacier,  on 
the  contrary,  are  carried  along  on  its  back  with- 
out undergoing  any  such  friction.  Lying  side  by 
side,  or  one  above  another,  without  being  subject 
to  pressure  from  the  ice,  they  retain,  both  in  the 
lateral  and  medial  moraines,  and  even  in  the 


EXTERNAL  APPEARANCE   OF   GLACIERS.        311 

terminal  moraines,  their  original  size,  their  rough 
surfaces,  and  their  angular  form.  Whenever, 
therefore,  a  glacier  melts,  it  is  evident  that  the 
lower  materials  will  be  found  covered  by  the 
angular  surface-materials  now  brought  into  im- 
mediate contact  with  the  former  in  consequence 
of  the  disappearance  of  the  intervening  ice.  The 
most  careful  observations  and  surveys  have  shown 
this  everywhere  to  be  the  case ;  wherever  a  large 
tract  of  glacier  has  disappeared,  the  moraines, 
with  their  large  angular  boulders,  are  found  rest- 
ing upon  this  bottom  layer  of  rounded  materials, 
scattered  through  a  paste  of  mud  and  sand. 

We  shall  see  hereafter  how  far  we  can  follow 
these  traces,  and  what  they  tell  us  of  the  past 
history  of  glaciers,  and  of  the  changes  the  cli- 
mates of  our  globe  have  undergone. 


THE  END. 


Cambridge  :  Stereotyped  and  Printed  by  Welch,  Bigelow,  &  Co. 


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